Short for Citizen's Band Radio. A wasteland inhabited by low-lifes, morons, bus drivers, truckers, and people who speak mangled Spanish at speeds you never thought imaginable. Almost impossible to use during the daytime in Miami, FL.
Then you have the morons who plug high power linear amplifiers into their CB radios and step on everyone else without mercy. Such people should be subjected to a needle in their coax. Generally frowned on by hams.