A closet fairy is a person who goes around telling random people they are gay. For any comeback, they use the word "gay."
Shut up, you are so gay!
Nah man, you're just a jealous Closet Fairy.
Dude, you are so gay. Who do you think you are?
A homosexual person who is still "in the closet" or not ready to reveal that s/he prefers members of his or her own gender.
Boy 1: Dude, John keeps looking at me in the locker room
Boy 2: Yea, he's such a closet fairy. He should just come out, already