A notification message returned to the sender by a site unable to relay e-mail to the intended recipient or the next link in a bang path. Reasons might include a nonexistent or misspelled user name or a down relay site. Bounce messages can themselves fail, with occasionally ugly results; see sorcerer's apprentice mode and software laser. The terms "bounce mail" and "barfmail" are also common.
Try this search on Wikipedia, OneLook, Google
Nearby terms: bottom-up testing « botwar « bounce « bounce message » boundary scan » boundary value » boundary value analysis