Longman Dictionary of Contemporary English - boo

~1 v 1 to shout `boo' to show that you do not like a person, performance, idea etc  (Some of the audience started booing.) 2 boo sb off (stage) to shout `boo' until a performer leaves the stage  (His jokes were so bad he got booed off stage.) ~2 interjection 1 plural boos a noise made by people who do not like a person, performance, idea etc 2 a word you shout suddenly to someone as a joke in order to frighten them 3 wouldn't say boo to a goose an expression used to describe a shy, quiet person  (Christine wouldn't say boo to a goose.)