be off (one's) nut(redirected from be off their nuts)
be off (one's) nut
slang To be crazy and/or wacky. Usually used humorously. Don't listen to a word he says, he's off his nut! You're off your nut if you think that plan will work.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.