off key

Collins Concise English Dictionary © HarperCollins Publishers::

off key adjective , adverb (off-key when prenominal)

1. not in the correct key
2. out of tune
3. out of keeping; discordant

WordReference Random House Learner's Dictionary of American English © 2025

ˈoff-ˈkey,  adj. 

1. out of tune:
   an off-key song.
2. somewhat irregular, abnormal, or unsuitable.

adv. 

3. out of tune:
   sang off-key.

WordReference Random House Unabridged Dictionary of American English © 2025

off-key  (ôf′kē′, of′-), adj. 

1. deviating from the correct tone or pitch;
   out of tune.
2. [Informal.] somewhat irregular, abnormal, or incongruous.

• 1925–30