1. used to startle or frighten someone
2. used to express disapproval or contempt

1. a sound made to startle or frighten
2. a shout of disapproval or contempt

1. to shout disapproval at a performer or speaker

Examples

• She jumped out and shouted ‘Boo!’ to scare her brother.
• The crowd began to boo the referee’s bad call.
• He couldn’t say boo to a goose.
• The actor was greeted with loud boos from the audience.
• Fans booed the visiting team throughout the game.
• Don’t boo the performers; they’re doing their best.
• The sudden boo from behind the door made me jump.