A young, relatively fit male who signs up for beginner-level YMCA exercise classes so he can hit on the better-looking girls and MILFs in a competition-free environment. Variation of "gigolo."
Guy 1: Hey, Mason, wanna go to the park and hoop like all the other dudes our age?
Guy 2: Naw, man, I've got a water aerobics class at 7:30, and Helen might be there now that her hip is better.
Guy 1: Oh my god, you're such a fucking Y-golo.