! A word used ironically in a situation where one might have scared someone, but said someone was not scared. Not said as loudly as in definition 1.
! An exclamation used by a member or many members of an audience, as at a stage play or sports game, to indicate derision or disapproval of what has just occurred.
n (US|slang) A close acquaintance or significant other, derived from French beau.
v (intransitive) To shout extended boos derisively.
v (transitive) To derisively shout extended boos at.