science fiction, sci-fi, S.F., SF, n. 1. in general usage, a genre of literary fiction exploring the effect of technological and scientific advancement (real or imagined) on humanity; term does not predate 1851. 2. fantasy literature in which fantastic or magical components are explained through imaginary science or technology. 3. (gamerese) a role-playing or wargaming milieu based upon or inspired by science fiction literature, or which explores similar themes. Also speculative fiction. [GJ1]