I'm surprised the
Pilot's Jargon series doesn't have this one...one way to 'squawk' is to set an
aircraft transponder to the
frequency or
code signal indicated. General aviation transponders in the US have a four digit
octal code setting, so 'squawking 1200' means to set the transponder to 1200. 'Squawk IDENT' means to push the button labelled 'ID' or 'IDENT' - which causes your blip on the radar screen to embiggen so that the controller can be sure they're looking at the right one. If a controller tells you to 'Squawk 3577 and ident' then...do both. Mode C and Mode S transponders (in the U.S. at least) squawk altitude, meaning that when they are set to 'ALT' and detect an
air traffic radar signal, they respond with a signal which includes their encoded octal number as well as the aircraft's current altitude. In an
emergency, a pilot should
squawk 7700 which means set his or her transponder to that set of digits so that it returns that code to
Air Traffic Control. This indicates that the aircraft is in distress.
The other meaning of 'squawk' is a report of something broken on the aircraft. If the pilot finds things not working, broken or unsafe during the inspection or during the flight, they will return a report (usually to whoever maintains the aircraft if it is not their own craft) with a list of 'squawks' on it.