be off (one's) rocker(redirected from be off their rocker)
be off (one's) rocker
To be crazy or mentally unsound; to be extremely foolish or foolhardy. I think Jane's grandmother is a little off her rocker these days. You must be off your rocker if you think that's a good idea!
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.