rhizoverbBeta
DictionarybooStartling cry
interjection

boo

A cry used to startle someone.

“Boo!” he shouts as he jumps from behind the curtain.

Etymology
bohMiddle Englisha loud, startling cry

Boo is a conventional vocal cry rather than a combination of historical roots. Its sudden, emphatic sound is used to surprise or frighten someone who is not expecting it.

More examples

  • The child whispers “boo” from beneath the blanket.
  • She startles her brother with a sudden “boo.”
  • The actor pops through the doorway and cries “boo!”