noun

• (aviation) A four-digit transponder code used by aircraft for identification or transmission of emergency signals.
• (informal) A complaint or objection.
  "That was the last roundup for McCutcheon’s Cresswell; it never moved from that field again. Not that there was any squawk from the landlord; the two of them owned it, of course."
• (aviation) An issue or complaint related to aircraft maintenance.
  "We think instructors should stress the importance of writeups on all maintenance squawks after the completion of each flight. More important, something should be done by the aircraft operator to correct such squawks."
• (programming, informal) A warning message indicating a possible error.
  "The function-hiding code above, for instance, goes through a different (but widely used) compiler with nary a squawk."

verb

• (slang, intransitive) To speak out; to protest.
• (slang, intransitive) To report an infraction; to rat on or tattle; to disclose a secret.
  ""I'll slit your throat if you squawk on us," Krantz threatened."
• (programming, intransitive, informal) To produce a warning message, indicating a possible error.
  "That way, if you type = instead of ==, the compiler will squawk because you can't assign something to a constant."
• (aviation) To set or transmit a four-digit transponder code. (Normally followed by the specific code in question.)
  "After discovering that the hydraulic system is faulty, the pilots squawked 7700 and declared mayday."