Mushroom Whelp Share definition Flag A mushroom whelp is the aftermath of being hit in the face from ones penis. Or the raised mark left from that act. After Sally ran her mouth, I gave her a mushroom whelp across her face. Mushroom Whelp by CoolerMan January 14, 2014 0 0 Get merch Get the Mushroom Whelp mug. Buy Now — $32.95 See more merch