Breadcrumb Home > Dictionary > Index R R factor: Meaning and Definition of Find definitions for: R factor Pronunciation: [key] a genetic component of some bacteria that provides resistance to antibiotics and can be transferred from one bacterium to another by conjugation. Also called Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. R.F.A. r.f.b. ✖ Related Content Daily Word Quiz: derogate Analogy of the Day: Today’s Analogy Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language