1. happy, joyful, positive. This
definition is rarely used, mainly in the phrase a gay old time.
2.
homosexual. Describes someone, usually a male liking other males, rarely a female liking other females, who is part of the LGBT community. See also: lesbian.
3. bad, stupid. This definition is only used by
douchebags and other idiots as they think insulting average people for being different is cool.