off one's rocker
idiomPart ofrocker
off one's rocker — idiom
1. Completely crazy or irrational; used informally to say that someone is acting in
1.idiom
Definition
Completely crazy or irrational; used informally to say that someone is acting in a very strange or foolish way.
Example
Talia's brother wants to climb the mountain in a thunderstorm wearing only flip-flops — he must be off his rocker.
Anyone who pays twenty thousand dollars for a rusty old car is off their rocker.