knock for a loop

knock someone for a loop 

1. Fig. to strike someone hard. You really knocked me for a loop. I hope that was an accident. DI was really knocked for a loop by the falling branch.

2. and throw someone for a loop Fig. to confuse or shock someone. (This is more severe and upsetting than throw someone a curve.) When Bill heard the news, it threw him for a loop. The manager knocked Bob for a loop by firing him on the spot.

See also: knock, loop

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knock/throw somebody for a loop  (American informal)

if something that happens knocks you for a loop, it upsets or confuses you because you do not expect it He knocked me for a loop when he said he was quitting his job.

See also: knock, loop