be off (one's) chump
be off (one's) chump
To be crazy. In the UK, "chump" is a slang term for "head." You're off your chump if you think that plan will work.
See also: chump, off
Farlex Dictionary of Idioms.
- chump
- off (one's) chump
- off one’s chump
- off your chump
- be off for (something)
- be off for sth
- (I've) got to take off
- browned off
- breeze off
- be off (one's) nut