1 definition by A-non-e-moose.
A girl who is only kept dangling by a guy whilst pursuing another, more attractive girl. Usually to have sex with when things go wrong.
My girlfriend was a "backup girl" before she met me.
"Are you dating her?"
"Nah man, she's just my backup girl."
"Are you dating her?"
"Nah man, she's just my backup girl."
by A-non-e-moose. October 20, 2008