/ Dictionary / Index G germ theory: Meaning and Definition of Find definitions for: germ' the"ory Pronunciation: [key] the theory that infectious diseases are due to the agency of germs or microorganisms. biogenesis. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. germproof germ warfare Related Content Daily Word Quiz: paradox Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language