(High school) Senior I'd Like to Fuck.
Similar in concept to MILF.
Despite sluts are possibly diseased, it doesn't stop me from fucking them. All I have to do is put on a rubber. If they're ugly, no brown paper bag or rubber. The hot sluts are always a SILFs.
Per an application (Naughty Gifts) on the facebook: a "Sheep I'd Like to Fuck"
On Brokeback Mountain, Jack's ass was not the only thing that Ennis lusted for. There were a multitude of SILFs to deflower and so Ennis brought a new "silence" to the lambs.
The abbreviation of "Sister I'd like to Fuck", used when a sister of someone is very hot.
Man, Tanner's sister is such a SILF