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knock somebody dead
to do something so well or look so attractive, other people admire you a lot Whenever Ella sang at a small club, she knocked â€™em dead.
Greatly amuse, astonish, or thrill someone, as in This new song will knock them dead. This slangy hyperbolic expression was first recorded in 1889. Also see knock the socks off.
1. To kill with a blow.
2. Slang To affect strongly and positively: a performance that knocked the audience dead.