off balance
1. Literally unbalanced or losing one's balance. This table is a bit off balance, I think one of the legs is shorter than the others. I always feel a little off balance when deboarding an airplane. I think it has something to do with the pressure.
2. Surprised or unprepared. Now that my kids are teenagers, they constantly keep me off balance with their antics.
off balance
1. Out of equilibrium, unsteady, as in When learning how to ride a two-wheeler, it's easy to get off balance and fall, or She stood up and threw the canoe off balance. [Mid-1900s]
2. Surprised, unprepared, as in The teacher gives unannounced tests to keep the class off balance. [Second half of 1900s]
(catch/throw somebody) off ˈbalance
1 make somebody/something unsteady and in danger of falling: I was thrown off balance by the sudden gust of wind.
2 make somebody surprised and no longer calm: The senator was clearly caught off balance by the unexpected question.