From Longman Dictionary of Contemporary Englishbuzzerbuzz‧er /ˈbʌzə $ -ər/ noun [countable] DTa small thing, usually shaped like a button, that buzzes when you press it Press the buzzer if you know the answer.
Examples from the Corpus
buzzer• In the vestibule, I scanned the column of buzzers while she fumbled in her purse for her keys.• They went into the lobby where the doorman, inordinately well-dressed to be pushing buzzers, gave I0C a sharp blast.• Each game she questions her ability anew, as if the starting buzzer erased all her past accomplishments.• Finally they rang the bell of the Frasers' flat, and after a moment the buzzer went.• I gingerly pressed the buzzer, embarrassed.• When the buzzer on the wall sounded she jumped, striking a wrong key.• When the buzzer went on his new chrome and ash desk, he jumped.• The buzzer sounded for the end of the quarter.• The buzzer on his intercom interrupted his thoughts. 