buzzer

/B AH1 Z ER0/
noun
  1. 1

    One who, or that which, buzzes; an insect that buzzes.

  2. 2

    A device that makes a buzzing sound.

    โ€œIf you think you know the answer to the question, hit the buzzer as fast as you can.โ€

  3. 3

    A police badge.

  4. 4

    A run scored from an overthrow.

  5. 5

    A gossip.

Source: https://en.wiktionary.org/wiki/buzzer