A towel used to soak up your jizz once you get turned on by something extremly sexy like blood on the dance floor or oldmen walking their tiny dogs while riding their scooters. A portable version of a jizz towel is the new and improved handy jizz rag.
Example one: "jarrod matthew is so amazing and his eyes are so yummy, I luvers him"
"jeez dude, get your fucking jizz towel ready"
Example two: -riding in the car- "HOLYWALNUTS! did you just see that bilboard with Morgan Freemen?!"
"dude... I got this handy portable jizz rag for you to use"