A gay man, whether on the down low, who seems like he is totally 100% straight but happens to enjoy having sex with men. Theses guys may play football, be captain of the baseball team, or be the lead in the musical people won't question their sexuality until they see that he's having the sex with a man.
Opposite: artificial fruit
Football player: Yo Darien, you coming to the party tonight? There's gonna be tons of hot chicks.
Darien: Nah man I'm a bromosexual, ya know? Haha good game, though.
Football player: Ah right man sorry I forgot.