1. A loud exclamation intended to scare someone, especially a child. Usually used when one has been hidden from the victim and then suddenly appeared unexpectedly.
2. 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.
3. 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.
1. a cry or noise made to express displeasure or contempt