shitlock smile
Derived from "shit eating grin" + "sherlock holmes". A smile one gives to another person when knowing something that other person might wish to know, but doesn't. A smug, slightly ugly smile usually given by a wanker, backstabber, or biatch. The person smiling may even look as if they wish to say, "It's no shit, Sherlock...that you're going down."
Lily: "Uh oh, Kayla.... Did you see Missy's shitlock smile? You'd better watch your back." Kayla: "Well naturally the brown stuff has to run off the nose down to the mouth...."
By kero frangipani pants