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knock (one) cold
1. To strike someone so hard that they lose consciousness. Yikes, that punch knocked the boxer cold.
2. To strongly impress someone. I'm sure she'll knock them cold in the audition. Your design is going to knock the judges cold. They're going to swoon over it.
knock someone cold
1. Fig. to render someone unconscious by a violent blow. One swipe, and he knocked him cold. If you touch her again, I'll knock you cold.
2. and knock someone dead Fig. to put on a stunning performance or display for someone. (Someone is often replaced by 'em from them.) This band is going to do great tonight. We're going to knock them dead. "See how your sister is all dressed up!" said Bill. "She's going to knock 'em cold."
To render unconscious; knock out.