look up any word, like fleek:
 
1.
One Size Fits Most (A more accurate version of the saying: One Size Fits All)
Dude 1: Do condom come in different sizes or OSFM?

Dude 2: OSFM. Except magnums are bigger if you packin' heat.
by tacticalhampster September 28, 2012
 
2.
Oh Shit Fuck Me
OSFM i forgot my sweater at home.
by XMIGGY January 24, 2012