Cumster Share definition Flag Mix of cum and dumpster. A person who likes to intake a large amount of semen at the same time. "Man Stacy's such a slut." "Really?" "Yeah. She a big fuckin' cumster". Cumster by Cool Guy 198712436 January 18, 2020 0 0 Get merch Get the Cumster mug. Buy Now — $32.95 See more merch