be (as) mad as a hatter
(redirected from are mad as a hatter)be (as) mad as a hatter
1. To be crazy. Tim has been behaving very erratically lately, so I'm afraid that he's as mad as a hatter.
2. To be very angry. Mom was mad as a hatter after I dented her brand-new car.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.