The opposite of a boy, not a girl. As the opposite of a girl is an anti-boy.

Gender is on a spectrum, and isn't limited to 2 genders. Of which in the spectrum an anti-boy is the polar opposite of a girl. Such as how a demi-boy is the opposite of a guy.
Dude, I was ERPing with this girl and it turns out they're an anti-boy, totally ruined my drive.
by uberspook June 15, 2017
A person who likes or respects real and talented music...
A talented musician once said "I hate Soulja Boy" i'm an Anti-Soulja Boy
by Free Press December 20, 2008