filthy 5k Share definition Flag Running a 5k and then immediately proceeding to receive oral, leaving your sweating crotch stench all over your partners face. I surprised my girl with a filthy 5k and she threw up all over my nuts. filthy 5k by anonymous October 15, 2020 0 0 Get merch Get the filthy 5k mug. Buy Now — $32.95 See more merch