Two options on what is meant: from the Urban Dictionary, (may be better than some folks sketchy definition of a liberal).

:))

""Liberal -
Somehow, it has turned into an insult, like the word conservative. Usually used as such by people who have never taken a political science class and don't know what the word means.

If used in a non-political sense, "liberal" simply means "a lot."I'd like a large popcorn with a liberal amount of butter, please.""