cum tum Share definition Flag When someone is constipated after having sex because of swallowing too much cum. Girl: Doctor I have a stomach ache. Doctor: Did you have sex the past day? Girl: Yes. Doctor: It sounds like a classic case of cum tum! cum tum by Stonewoof December 20, 2015 0 0 Get merch Get the cum tum mug. Buy Now — $32.95 See more merch