What is a gay keester?

A popular term referring, in general, to the ass, though mainly a reference to the fleshy part of the rear end. The Buttocks. Can also refer to the anus.

Definition

The origins of the word is obscure, but it used to refer to a case, or satchel in the mid 1800's. Also believed to be derived from various words, meaning chest or container.

Also a 'Yiddish' term popularized to refer to a person, a bum.