A job you take knowing that it isn't long term. Often due to an emergency situation where you know your losing your current job. It provides a paycheck while you take your time looking for a better job.
Starbucks was totally a rebound job, I was minutes from getting fired and needed something fast!
A job you take when you've recently lost or feel you are about to lose another (usually better) job. The rebound job is likely not in one's chosen career path, and often its only purpose is for the worker to earn money while searching for a more suitable (better paying/career-advancing) position.
Waiting tables is just my rebound job, since I was just layed-off from a great Marketing company. I've gotta pay the bills until I can find another good Advertising job!