What is Squawk?

A squawk is the four-digit transponder code assigned to an aircraft; the word is also used for a reported aircraft defect.

In its primary sense, to "squawk" is to set a four-digit code (0000–7777) on the aircraft transponder so that air traffic control can identify the aircraft on radar. Some codes are reserved, such as 7700 for an emergency and 7600 for radio failure.

In maintenance use, a "squawk" is also informal slang for a reported defect or snag that needs attention before the aircraft flies again.