knock someone for six
BRITISH, INFORMALCOMMON
1. If something knocks you for six, it shocks or upsets you so much that you have difficulty recovering. The emotional impact of losing a parent can knock you for six.
2. If an illness knocks you for six, it causes you to be very ill and weak for a long time. I picked up a virus that knocked me for six. I lost a stone in weight in two weeks.
3. If someone knocks you for six, they impress you to a very great degree. One day Gary walked in with his sister, Leah, and I was absolutely knocked for six. I'd never seen such a beautiful woman. Note: In cricket, six runs are scored when a batsman hits the ball so that it lands outside the playing area without bouncing. When this happens, you can say the bowler has been hit for six.