What does a sitter mean in gay sex?

What is sitter?

A term to refer to a prostitute who works a bar or nightclubs.

Definition

Naturally can also refer to inactive person, who prefers to sit on their buttocks, than be active. Dated term to call a male who will flash a wad of money, in a bar or nightclub. This is to signal that they are seeking company, and are willing and able to pay for that service.

In drug parlances', can be someone who sits with a person, who is using LSD for their first time, to insure they don't do something foolish.