Dic: off balance

• Policy makers were caught off balance by the speed and success of Canada's efforts to ban the weapons.
• A gust of wind knocked him off balance and he fell face down in the mud.
• She was trying to behave as if his visit hadn't thrown her off balance.

1. off balance: surprised or confused.

• Usage notes: often used with keep or throw:
  
  The stories were part of an effort to keep the antiwar movement off balance.
  
  
• Etymology: based on the literal meaning of off balance (likely to fall)

2 (1) PHRASE : PHR after v, v-link PHR | If you are off balance, you are in an unsteady position and about to fall. (2) PHRASE : PHR after v | If you are thrown off balance by something, you are surprised or confused by it.

.... Cambridge Dictionary of American Idioms, Cobuild