It literally just means "suck my tits"
Usually, girls with small or big tits say this, no in between. Occasionally men say this.
(If a girl says this to you all you gotta tell them is "But you've got none"
They will immediately either walk off embarrassed or knee kick u in your balls/stomach)
Abbie: Bro why do you always say the dumbest shit?
(Some girl) : Stfu smt I'm smarter than your dumbass.
(v.) acronym for 'Shake My Tail'; in relates to puppies. Usually used by puppies when they are disapointed or when something stupid is being said or done. Also SMFT or SMMFT
Coco (puppy): "The devil created you"
Xzavier: "i know this" said being sarcastically
Coco (puppy): "SMT"