A towel that is usually "recycled" by being hung up to dry for the next person to use. It becomes a taint towel after a man uses it in a "flossing motion" to dry his private parts after a shower. The next person, not aware of the residue left on the now-dried towel, uses it to dry off.
Roommate 1: *Thoroughly dries his groin area in every nook and cranny. Then he hangs up the towel.*
Roommate 2: *Dries himself off after his shower*
"Hey, the towels in the bathroom don't smell too great. Did you remember to use detergent?"
Roommate 1: "Haw haw, you just got a face full of taint towel!!"