not know what hit you

US /nɑt noʊ wʌt hɪt ju/
UK /nɑt noʊ wʌt hɪt ju/
"not know what hit you" picture
1.

何が起こったのか分からない, 完全に不意を突かれる

to be completely surprised or overwhelmed by something, often something negative or sudden

:
When the market crashed, many investors didn't know what hit them.
市場が暴落したとき、多くの投資家は何が起こったのか分からなかった
The boxer landed a punch so fast, his opponent didn't know what hit him.
ボクサーはあまりにも速いパンチを繰り出し、相手は何が起こったのか分からなかった