abbreviation of 'search the fuckinginternet', sometimes used in games when somebody askes a dumb question which he could easily look up on the internet
Person 1: "Where do I start this quest?"
Person 2: "STFI!!"
An acronym used during election year, and more precisely on election day. It stands for Stay The Fuck In Line. It represents a commitment to vote on election day no matter what.
Hey buddy, don't get confident that the democrats will win this year and go home, STFIL!