S.L.U.T. Share definition Flag Sweet Little Unforgettable Thing. Commonly used when someone calls a girl a slut, but decides to be sneaky about it. "You're such a Sweet Little Unforgettable Thing." <--Read: S.L.U.T. "Awww thanks!" *laughter* S.L.U.T. by hawtxpink February 26, 2011 0 0 Get merch Get the S.L.U.T. mug. Buy Now — $32.95 See more merch