Church mouse: Refers to a poor person or someone who is meek and quiet.

A goth who has been part of the subculture since it originally came about, or a goth over the age of 40.

A church mouse is a meek individual who attends church regularly and frequently.

a mouse that is in church

is when a fellow friend is wearing shorts (or pants, yikes) and sneaks the tip of his penis out the bottom of his pants..

used in the sense of a "made-ya-look" phrase

A dude that sucks another dudes dick on the down low and keeps his mouth shut about it

A church mouse is a mouse that lives in a church, but in slang, it means a dude with a very small dick; a micro penis.