boo

Short definition from Wiktionary

Interjection

1. 1
   A loud exclamation intended to scare someone. Usually used when one has been hidden from the target, and then appears unexpectedly.
2. 2
   An exclamation used by a member of an audience, as at a stage play or sporting event, to indicate derision or disapproval.

Noun

1. 1
   A derisive shout made to indicate disapproval.
2. 2
   A close acquaintance or significant other.
3. 3
   Cannabis.
4. 4
   A tail feather from an ostrich.

Verb

1. 1
   To shout extended boos derisively.
2. 2
   To shout extended boos at, as a form of disapproval or derision.
3. 3
   To make a sound characteristic of cattle; to moo.

Proper noun

1. 1
   A community in Nacka, Stockholm, central Sweden.
2. 2
   The Boko language.