The part of the spectrum dedicated by the US Federal Communications Commission to unlicensed radio transmissions, mostly among truckers. Also known by its initials, CB.

There are 40 channels on CB radio. Channel 9 is reserved for emergencies only. Channel 19 is the most general forum, where most people hang out. Private conversations belong on other channels, although of course privacy consists of other people's willingness to shut up on a channel that's in use and not to eavesdrop. Newbies who don't speak CB lingo, or speak a 70's dialect, might be told to take it to channel 41. The assumption is that they haven't yet learned there are only 40 channels.