The act of a ejaculating at the precise moment when a man initiates his bowel movement. This is a very difficult task and should be attempted with great caution.
Dan: Hey dude, is it possible to have an orgasm while pooping?
Joe: I don't know, go try.
Dan: Would that be considered shumming?
Joe: Yes.
The profound sense of shame that accompanies an ejaculation during intercourse with a partner whom the ejaculater knows he or she does not respect or wish to be involved with for a long time, despite said partner's false perception that the relationship extends beyond intercourse; to cum with shame.
She was so shallow, vain, and dumb, but so busty that I couldn't help but let myself shum into her foul mouth.