Noun

1. A shrill noise, especially made by a voice; a yell, scream, or call.
2. (Aviation) A 4-digit transponder code used by aircraft for identification or transmission of emergency signals.
3. (Aviation) An issue or complaint related to aircraft maintenance.

Verb

1. To make a squawking noise; to yell, scream, or call out shrilly.
2. To speak out; to protest.
3. To report an infraction; to rat on or tattle; to disclose a secret.