The dictionary simply says, “a person who loves parties,” but there are several kinds of parties. Somehow, I don’t think that a woman who enjoys going to elegant formal dinner parties could be called a party animal, even though it would align with the definition in the dictionary.
I think it refers to something more along the lines of when we stay up too late. Am I right?
At least in the U.S., the term is usually used to describe people who go to wild and raucous parties, and to those who enjoy that lifestyle.
It’s not necessarily tied to being out too late, although many “party animals” do often stay out way past a normal bedtime.