upchuck muff Share definition Flag Upchuck muff is when an individual is eating out a woman and throws up in her vagina. "Dude, I was with this girl last night after leaving the bar and, well, lets just say she has an upchuck muff." upchuck muff by Upchuck muff mike February 24, 2018 0 0 Get merch Get the upchuck muff mug. Buy Now — $32.95 See more merch