Cumster Share definition Flag Combination of Cum and Dumpster. A person (usually a woman) that uses her body for men to unload millions of potential children. Dude, Lisa is a real Cumster. She always shows up on circle jerk night. Cumster by Hexx5150 November 23, 2009 0 0 Get merch Get the Cumster mug. Buy Now — $32.95 See more merch