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

Radio Regulations
The latest ITU Radio Regulations to which the United States is a party.

RACES
(radio amateur civil emergency service). A radio service using amateur
stations for civil defense communications during periods of local,
regional or national civil emergencies.

Reflected power
Non-radiated power dissipated as heat when the transmitter is mismatched
to the antenna or load.

Rain locker
Slang for a bathroom shower.

Remote control
The use of a control operator who indirectly manipulates the operating adjustments in the station through a control link to achieve compliance
with the FCC Rules.

Repeater
A system consisting of at least one transmitter, one receiver, and a controller, which receives a signal on one frequency and retransmits it
on another frequency. Repeaters are typically located in high locations
so that they have greater coverage area. They greatly increase a user's communication range since they can retransmit his/her signal across all
of its coverage area. Repeaters are in geographically high locations,
and are most commonly used on the 2 meter and 70 centimeter bands. See
also "Simplex Repeater".

RF
"Radio Frequency"; typically used as slang for "Radio Frequency Energy".

RF Burn
A painful sensation felt when coming into direct contact with RF energy;
can be dangerous when experienced with high levels of RF power.

RF ground
Connection of amateur radio equipment to earth ground to eliminate
hazards from RF exposure and reduce RFI.

RFI
Radio Frequency Interference

Rig
Slang for Radio

RIT
"Receive Incremental Tuning"; a common feature on HF radios that allows the user to slightly change the receive frequency while leaving the transmit frequency the same.

RST
"Readability, Strength, Tone"; a system by which a received signal quality
is graded, and a signal report is given. "Readability" is judged on a
scale from 1 to 5, and "Strength" and "Tone" are judged on a scale from
1 to 9. "Tone" does not apply to a "phone" (voice) signal. A very high
quality CW signal is "599" (pronounced "five nine nine"), and such a phone signal is "59" (pronounced "five nine").

RTTY
"Radio Teletype"; popular digital mode on HF

Rubber Duck
Also known as "Rubber Duckie", a flexible antenna normally found on
hand-held tranceivers. Inefficient, but useable, and they don't poke you in
the ribs too badly either! (thanks to WD5CTQ).

RX
Abbreviation for "receiver" or "receive".
--- SBBSecho 3.20-Win32
* Origin: The Thunderbolt BBS - Little Rock, Arkansas (316:36/9)