a person in a relationship that is used by the opposite person as an emotional or romanticcrutch when their partner, or spouse doesn't provide for their emotional needs.
James:So hows the new girl going?
Josh: Oh, great...but she has a boyfriend.
James:Dude, don't be her rebound!
When fighting another person, if you get knoced down to the ground, you get back up and start fighting even harder than before, and you kick the other persons ass.
During the fight yesterday Adam got knocked down but he won the fight with a rebound.