Acronym for "Alien I'd Like to Fuck".
A crucial staple of Science Fiction, rendering it watchable.
Pronounced "alf", but not to be confused with the puppet from the 1980s TV show, who is not an example of an AILF.
Examples of an "AILF":
The chick Steve Guttenberg does (in an alien sort of way) in "Cocoon".
Natasha Henstridge is "Species".
"Orion slave girl" (the green chick) in "Star Trek".
Dude 1: Hey did you see those ailfs in Fast and Furious: Tokyo Drift?
Dude 2: Yes I jacked off in the theater to those ailfs. Damn I gotta get me some of that good stuff, yo.