imp. Acronym for 'Read The Fucking Manual'. 1. Used by gurus to brush off questions they consider trivial or annoying.
Compare Don't do that, then!
2. Used when reporting a problem to indicate that you aren't just asking out of randomness.
"No, I can't figure out how to interface UNIX to my toaster, and yes, I have RTFM."
Unlike sense 1, this use is considered polite.
The variant RTFS, where S = 'Standard', has also been reported.