Muscle of the anal opening. Can be easily ruptured through violent anal sex.

A stupid person; it refers to the lack of surface area on an individual's brain. The general thought is that the more surface area (wrinkles, creases, etc.) a brain has, the smarter the person is. Conversely, a person with a smooth brain (no wrinkles) has less surface area and would therefore be stupid.

The seal around a person anus.

1. (slang) sphincter
2. (normal) a rubbery gasket used to seal a connection between two pipes. The o-ring is squished between two flanges, forming an air-tight seal.

your brown eye, bunghole, or the muscle that holds your turtle head in.

Anal muscles.

a round seal, often made of neoprene or some other compressible "rubber-like" compound, that is an industrial part.Looks like the part of a condom that unrolls before you actually unroll it. Can be used as a cock ringif you get the right size