Horse's Tail Share definition Flag When a girl lets the hair around her anus grow out to a much too lengthy length, thus resembling the tail of a horse! I tried to go down on Peggy last night but her horse's tail kept tickling my chin! Horse's Tail by bob2468 December 22, 2009 0 0 Get merch Get the Horse's Tail mug. Buy Now — $32.95 See more merch