Fast ass is usually a girl that tries to act like she is too damn grown.

A cultural and aesthetic mind-state that prioritizes making money, even as an “underground” or “radical” creator. The work isn’t made for money, but it’s the money that matters the most.

someone who gives it up too fast or is easy

It means precocious. It does not necessarily mean whore or easy, as defined in the previous definition. It particularly applies to young girls

Term for men, of any sexual preference, who fuck to fast

Or indeed it could be used for a lady, wearing a strap-on and going for it in a fast manor.