Several meanings.
1. A person who doesn't take things seriously/a childish and irresponsible person.
2.
Homosexual
Used as an
insult; not necessarily directed towards a person who practices this lifestyle, but as a synonym for wuss/pussy/
chicken.
1. Seinfeld Ep22 (S03E05) - The Library
Bookman (talking to Jerry) : You and your good-
time buddies. Well I got a flash for ya, joy-
boy: Party time is over. Y'got seven days, Seinfeld. That is one week!
2. Sadistic gym teacher : You still got 3 more laps, get moving, joy-
boy!