off (one's) dot
off (one's) dot
Crazy or mentally unsound; extremely foolish. I'm going to go off my dot if I have to hear that blasted song once more! I think Jane's grandmother is a little off her dot these days. You must be off your dot if you think that's a good idea!
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.