From QRZ.Com, the Icom handout, and Part 97 Of The FCC Rules -
Ham Radio Glossary - An overview of amateur radio terms.

m. Meters.

Machine
Slang for "repeater", and sometimes for rig.

MARS
Military Affiliate Radio Service

Matchbox
A device placed between a transmitter and an antenna to tune the circuit
to resonance. Normally called an Antenna Tuner (thanks to WD5CTQ).

Mc
"Megacycle"; equivalent to MHz; regarded as an "old fashioned" way of describing frequency.

Medfer
One who experiments with radio communications at low frequencies such as
those on the edges of the AM broadcast band (under FCC Part 15).

Memory bank
A set of memory channels organized into a group.

Memory effect
Rechargeable batteries such as Ni-Cad (Nickel Cadmium) and Ni-MH
(Nickel Metal Hydride) types may be temporarlity getting less
capacity/usage as a result of repeated non-full charge/discharge
cycles. It is called so sinc rechargeable batteries lose capcity
as if "memorize" wrong full capacity level at less than full charge.
Li-ion (Lithium Ion) batteries are free from this effect.

Message forwarding system
A group of amateur stations participating in a voluntary, cooperative, interactive arrangement where communications are sent from the control
operator of an originating station to the control operator of one or
more destination stations by one or more forwarding stations.

MF
(medium frequency). The frequency range 300-3000 kHz.

MHz
See Hz

MIC
Microphone

Modulation
Method of adding information to a radio frequency carrier.

MPR
"Mass Produced Rig"; a radio which is produced in large quantities; often
used to describe radios that are NOT originally purchased in "kit" form.

MUF
"Maximum Useable Frequency"; that frequency above which expected
propagation no longer exists.
--- SBBSecho 3.20-Win32
* Origin: The Thunderbolt BBS - Little Rock, Arkansas (954:895/7)