A system for receiving beacon signals and rebroadcasting them on the same frequency to confuse navigation.
The sum of all values in the data, divided by the number of values.
Mean Effective pressure
The mean or average pressure which, acting on the piston, would do the same work as does the actual variable pressure in the cylinder.
Mean Free Path
For sound waves in an enclosure, it is the average distance travelled between successive reflections.
Mean Piston Speed
The average speed of the piston in the cylinder bore.
Mean Sea Level
The average relative sea level over a period, such as a month or a year, long enough to average out transients such as waves.
Mean Stress
Algebraic difference between maximum and minimum stress in one cycle of fluctuating loading, as in a fatigue test.
Mean Time Between Failure
The average time between failures for a continuously operating system.
Mean Time to Failure
The measured operating time of a system or component divided by the number of failures that occurred during that time.
A physical quantity, force, property or condition which is to be measured.
The collection of quantitative data.
Equal to two to the power of twenty bytes.
Mechanical Efficiency
The ratio of brake horsepower to indicated horsepower.
Mechanical Energy
Energy in a mechanical form.
Mechanical Energy Storage
The storage of energy in a device such as a spring.
Mechanical Engineer
An engineer who applies the principles of mechanics and energy to the design of machines and devices.
Mechanical Engineering
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Mechanical Filter
A device to remove dirt and other impurities from air, oil, or water.
Mechanical Fuel Injection
Injection with the fuel-valve operated mechanically from a cam.
Mechanical Impedance
The mechanical properties of a machine system (mass, stiffness, damping) that determine the response to periodic forcing functions.
Mechanical Properties
The properties of a material that reveal its elastic and inelastic behaviour where force is applied.
Mechanical Seal
A device which works to join together systems or mechanisms in order to prevent leakage, contain pressure or exclude contamination.
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Mechanics Vice
A workshop tool, firmly mounted at a convenient height for holding and gripping material while working on it.
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Rigid bodies connected by joints in order to accomplish a desired force and/or motion transmission.
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The introduction of electronic controls into mechanical components.
Medial Triangle
The triangle whose vertices are the midpoints of the sides of a given triangle.
A statistic which measures the centre of a set of data by finding that value which divides the data in half.
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The vehicle through which a wave travels from one point to the next.
Medium Altitude Orbit
An orbit from 2,000 to 12,000 miles above the earth.
Medium Frequency
The portion of the electromagnetic spectrum between 300 kHz and 30,000 kHz.
Medium Voltage
AC system operating voltages from 601 to 15000 VAC.
Prefix representing a multiplication of 106
One megabarrel equals 42 million U. S. gallons.
One million bytes. A megabyte is a unit of information content equal to 1,048,576 bytes.
One million cycles; one thousand kilocycles.
One million floating-point operations per second.
One million parsecs.
One million watts.
MegaWatt hours
A unit of energy equal to 1,000,000 watts for one hour.
One million ohms.
Process of cellular division which produces egg or sperm cells.
Meissner Effect
The decrease of the magnetic flux within a superconducting metal when it is cooled below the transition temperature.
Meitner, Lise
Physicist who collaborated with Otto Hahn to discover protactinium and with Hahn and Fritz Strassmann to accomplish the fission of uranium.
A proportional scale, in which equal intervals correspond to equal perceived interval sizes.
The mineral name for Iron II Sulphate.
Melt Flow Index
Measure of how many grams of polymer pass through a standardized capillary under a standard load over 10 minutes. The value obtained through the melt flow index test is a single data point.
Melting Point
The temperature at which a solid substance changes to a liquid state.
Melting Range
The temperature range between solid and liquid.
A thin sheet or layer.
Membrane Structure
A shell structure, that does not take wall bending or compression loads.
In a computer system memory is used to store data temporarily or permanently. The capacity of the memory is normally measured in bytes.
Abbreviation of Micro Electro Mechanical Systems.
Mendel, Gregor Johann
An Austrian scientist and monk who described the inheritance of garden peas in a paper entitled Experiments in plant hybridization.
Mendeleev, Dmitri Ivanovich
Russian chemist; developed the periodic table by placing the elements in order of increasing atomic weight.
Man-made element with an atomic number of 101.
The curved surface of a liquid in a container produced by the cohesive forces between the liquid molecules and the adhesive forces between the liquid and the container.
The measurement of lengths, areas and volumes.


A waxy, crystalline substance, clear or white in color, which is solid at room temperature and melts slightly above.

The group of atoms that constitutes a polymer chain repeat unit.
Mercalli Scale
A measure of the intensity of an earthquake. This is a subjective value that varies depending on where the earthquake is observed.
Mercuric Chloride
Another name for Mercury II Chloride.
Mercuric Oxide
Another name for Mercury II Oxide.
Mercuric Sulphide


The ore of mercury. Occuring as red crystals.

Mercurous Chloride
Another name for Mercury I Chloride.
The planet nearest to the sun in our solar system.
Mercury Barometer
Consists of a closed tube filled with mercury inverted in a mercury reservoir.
Mercury Dichlorate
Another name for Mercury II Chloride.
Mercury Hg
The most common liquid metal at room temperature.
Mercury I Chloride


Dense white or yellowish-white odorless solid. It was used in medicine as a diuretic and laxative although this is now discontinued.

Mercury II Chloride


One of the most toxic forms of Mercury.

Mercury II Oxide


A red or orange solid at room temperature that is used in the production of Mercury as it decomposes readily.

Meridional Flow
Atmospheric circulation in which the north and south, or meridional, component of motion is unusually pronounced.
Mersenne Number
A number of the form 2p-1 where p is a prime.
Mersenne Prime
A Mersenne number that is prime.
To engage as the teeth between two gears.
Meso Compound
A compound that has two or more chiral centres but does not rotate plane-polarized light because it has an internal plane of symmetry.
A distribution that is normal.
Mesomeric Effect
Another name for Resonance Effect.
A type of hadron with whole-number units of spin.
Extremely cold region of the earth′s atmosphere at an altitude of approximately 80 km, representing the boundary between the mesosphere and the overlying thermosphere.
A pore of diameter from about 2 nm to 50 nm.
A zone in the Earth between 400 and 670 km below the surface separating the upper mantle from the lower mantle.
The geological era covering about 245 million years ago to 65 million years ago.
Messenger RNA
Synthesized in the nucleus in a process called transcription using a DNA segment as a template.
Messier, Charles
18th century French astronomer who compiled a list of approximately 100 fuzzy, diffuse looking objects which appeared at fixed positions in the sky.
Mestral, George de
Swiss engineer who invented Velcro.
A sequence of biochemical reactions that converts fuel molecules into energy used to drive other biological processes.
A compound produced by metabolic reactions.
A metal is a substance that conducts heat and electricity, is shiny and reflects many colors of light, and can be hammered into sheets or drawn into wire.
Metal Alloy
Metal blended with some other metallic or non-metallic substance to give it special qualities.
Metal Inert Gas Welding
Filler rod as a consumable electrode, and the rod is automatically fed.
Metal Matrix Composite
A composite that uses a metal as the matrix phase.
Metallic Bond
A primary interatomic bond involving the nondirectional sharing of nonlocalized valence electrons which are mutually shared by all the atoms in the metallic solid.
Metallic Compound
Compound that contains at least one metallic element.
Metallic Radius
The atomic radius from as established by measuring the distances between atoms in metallic crystals.
A protein having a metal ion as its prosthetic group.
The science and technology of metals and alloys.
In a MOSFET device the gate is insulated from the channel by a very thin (typically less than the wavelength of light) layer of glass (silicon dioxide) and the gate is either metal or doped silicon (polysilicon), hence the acronym metal-oxide semiconductor.
Metalworking Lubricant
A liquid used to cool and lubricate the cutting to improve the work surface finish.
Nonequilibrium state that may persist for a very long time.
A meteoroid that has entered Earth′s atmosphere.
Meteor Burst Communications
A telecommunication technique which uses meteor activity in the ionosphere as a mechanism for reflecting short data transmissions from field sites to a base station.
Meteor Shower
A number of meteors with approximately parallel trajectories.
Meteor Stream
A group of meteoric bodies with nearly identical orbits.
The remnants of a meteor after it has actually impacted the Earth.
A collection of automatic meteorological recording instruments, often times describing the package that is carried aloft on an instrument platform.
An object in space similar to but smaller than an asteroid.
Of or pertaining to atmospheric phenomena, especially weather and weather conditions.
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A device used to measure a specific quantity, such as current, voltage, or frequency.
Meter Movement
The part of the meter that moves to indicate some value.
Meter Shunt
A resistor placed in parallel with the meter terminals; used to provide increased range capability.
Metering Jet
A jet in a fuel-injection system that controls the fuel flow rate.
Alternative name for Formaldehyde.
The first alkane. Occurs naturally as marsh gas and in oil wells.
Methane Recovery
Method by which methane emissions are captured and then reused either as a fuel or for some other economic purpose.
Methane Trichloride
Alternative name for Chloroform.
Methanoic Acid


Most famous for it's occurrence in Ant and Bee venom.

A colourless liquid also known as methyl alcohol.
Methenyl Trichloride
Alternative name for Chloroform.
Alternative name for Dimethyl Ether.
The name of a wine bottle equivalent to the volume of 8 standard bottles or 6 litres.
The monovalent radical -CH3
Methyl Acetate


A clear, flammable liquid with a characteristic, not unpleasant smell like certain glues or nail polish removers.

Methyl Alcohol
Also known as methanol.
Methyl Bromide
Alternative name for Bromomethane.
Methyl Chloride
Alternative name for Chloromethane.
Methyl Cyanide
Also known as Acetonitrile.
Methyl Ethanoate
Alternative name for Methyl Acetate.
Methyl Ether
Alternative name for Dimethyl Ether.
Methyl Phenyl Ether
Also known as Anisole.
Methyl Tertiary Butyl Ether
A fuel oxygenate used as an additive to gasoline to increase octane and reduce engine knock.

Methyl Trichloride
Alternative name for Chloroform.
Also known as toluene.
Methylene Chloride
Alternative name for Dichloromethane.
Methylene Dichloride
Alternative name for Dichloromethane.
Metonic Calendar
Based on the moon, counting each cycle of the phases of the Moon as one month.
The metre is the SI unit of length.
Metre Kilopond
Metric unit of torque equal to 9.806 65 newton metres (Nm) or 7.233 01 pound feet.
Metric Completeness
A metric space is complete if all Cauchy sequences of its elements converge.
Metric Horsepower
Also known as Cheval Vapeur.
Metric Ounce
A unit of mass, equal to 25 grams. Also known as a mounce.
Metric Pound
An informal name for a mass of 500 grams.
Metric Sabin
This is the product of surface area and absorption coefficient. Therefore, the absorption within a room may be specified by a single number. One metric sabin is the equivalent to one square metre of a perfectly absorptive surface.
Metric Second
Also known as a blink.
Metric Space
A space X is metric if there is defined a real non-negative function of two variables d(A, B).
Metric System
The international decimal system of weights and measures based on the metre and the kilogram.
Metric Threads
Tapping and clearance drill sizes for coarse and fine metric thread sizes.
Metric Ton
Through common usage the 1000kg has been named the Tonne.
The science of dimensional measurement; sometimes includes the science of weighing.
One million electron volts.