off-the-wall

[awf-th uh-wawl, of-] /ˈɔf ðəˈwɔl, ˈɒf-/

adjective, Informal.

markedly unconventional; bizarre; oddball:

an unpredictable, off-the-wall personality.

Origin

1970-75

Examples from the web for off-the-wall

Have the people who practice with you ask you both predictable and off-the-wall questions.
It is certainly not an eccentric or off-the-wall position.
These business predictions are a little more off-the-wall and specific than we've done in past years.
off-the-wall comedy flourishes in out-of-the-way places.
If you're using some off-the-wall word processor, the printer selection option may be found somewhere else.

British Dictionary definitions for off-the-wall

adjective

(off the wall when postpositive) (slang) new or unexpected in an unconventional or eccentric way: an off-the-wall approach to humour

Word Origin

C20: possibly from the use of the phrase in handball and squash to describe a shot that is unexpected