When a guy is on break or has recently broken up with his girlfriend and tries find a replacement. The new girl will probably fall for him. Then he goes back to his old girlfriend leaving the other girl in the dust, or "ducking" her.
The "replacement" girl got Ducked.
Girl 1: So what ever happened to what's his name?
Girl 2: Oh he Ducked me, for real. He went back to his ex.
Girl 1: Oh girl that sucks. Lyin', Cheatin', huzzies always get the good ones.