STFD is an acronym to simply say SLOW THE FUCK DOWN. This wonderful acronym comes from a musical called Come From away which I suggest you check out.
And if they're speedin', I'll stop them and write out a warning ticket. I'll write STFD
Slow the fuck down!
WHEN YA GIRL ASK FOR A DATE AND YOU DONT FEEL LIKE SPENDING MONEY ON HER SO "STFD"
STFD or in other words, sit the fuck down
a definition like for an example,
m8 STFD B4 i slap u mike.
u want some m8?
abbreviation for 'sit the fuck down'
"woah, that joke went too far, stfd!" or (just after you win an argument "Yeah, that's what I thought... now stfd..."