Plain English Meaning
A radio frequency (122.9 MHz) that pilots use to talk to each other when flying into or out of a small airport that has no control tower and no ground radio station of its own.
Full Definition
A mobile aeronautical service performed on the frequency 122.9 MHz to provide air-to-air communications between pilots operating at airports that have no tower, no Flight Service Station, and no published Unicom frequency.
Context Anchor
Seen in airport information listings and used by pilots at many small airports when announcing position, movement, or intentions.