Idiom meaning, usage examples, facts

1. Mrs. Crowell is convinced she sees ghosts in the halls, and that they talk to her. I think she’s off her rocker.
2. You must be off your rocker to think that the boss will give you such a big pay raise. He hasn’t given anyone else a raise like that.

Compare to: bats in (one’s) belfry; out to lunch; screw loose. All of these expressions, including off one’s rocker, are used in a light-hearted, slightly humorous sense.