Sprouting from the words Tyrannosaurus "the King of Dinosaurs"
and fag "a homosexual", Fag-a-saurus Rex refers to a deeply homosexual man. One that lacks even the smallest amount of dignity, testosterone, or self-respect. The King of Fags.
John: Was that a chick with a dick ?
Wilson: Naw man that's just a fag-a-saurus rex.