1 definition by Sarah B.
acronym for: secret internet fatty.
molly: omg that girl is huge!
tina: i saw her pics on myspace, i thot she was skinny!
molly: wow what a sif!
tina: i saw her pics on myspace, i thot she was skinny!
molly: wow what a sif!
by Sarah B. August 7, 2007