/ Dictionary / Index M marathoner: Meaning and Definition of Find definitions for: mar•a•thon•er Pronunciation: (mar'u-thon"ur or, esp. Brit., -thu-nur), [key] — n. a runner who competes in a marathon. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: marathoner (Thesaurus) marathon marathon group Related Content Daily Word Quiz: belligerent Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language