THROW (OR KNOCK) SOMEONE FOR A LOOP N. AMER.
Meaning of THROW (OR KNOCK) SOMEONE FOR A LOOP N. AMER. in English
throw ( or knock) someone for a loop N. Amer.
informal
surprise or astonish someone.
→ loop
Concise Oxford English vocab.
Сжатый оксфордский словарь английского языка.
2004