The Collaborative International Dictionary of English v.0.48:

marathon \marathon\ n.
   1. A footrace of 26 miles 385 yards. [WordNet sense 2]
      [WordNet 1.5]

   2. Hence: Any long and arduous undertaking, straining the
      endurance of the participants. [WordNet sense 1]

   Syn: endurance contest.
        [WordNet 1.5]

   3. (Capitalized)a battle in 490 BC in which the Athenians and
      their allies defeated the Persians. [WordNet sense 3]

   Syn: battle of Marathon.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

marathon
    n 1: any long and arduous undertaking [syn: marathon,
         endurance contest]
    2: a footrace of 26 miles 385 yards
    3: a battle in 490 BC in which the Athenians and their allies
       defeated the Persians [syn: Marathon, battle of Marathon]

Moby Thesaurus II by Grady Ward, 1.0:

119 Moby Thesaurus words for "marathon":
   Arica movement, Erhard Seminars Training, Le Mans,
   New Consciousness, Pentothal interview, SAT, T-group, air race,
   assertiveness training, automobile race, behavior modification,
   behavior therapy, bicycle race, bioenergetics, biofeedback,
   boat race, confrontation therapy, conjoint therapy,
   consciousness raising, contest of speed, counseling,
   cross-country race, dash, derby, directive therapy, dog race,
   drag race, drawn-out, encounter therapy, endurance race, est,
   extended, family training, feminist therapy, footrace,
   gestalt therapy, group psychotherapy, group relations training,
   group sensitivity training, group therapy, heat,
   humanistic therapy, hurdle race, hypnoanalysis, hypnosis,
   hypnotherapy, hypnotism, interminable, languishing, lap, lasting,
   lengthened, lingering, long, long-continuing, long-drawn,
   long-drawn-out, long-pending, long-winded, marathon race,
   marriage encounter, match race, mind cure, motorcycle race,
   narcoanalysis, narcohypnosis, narcosynthesis, narcotherapy,
   nondirective therapy, obstacle race, occupational therapy,
   overlong, pastoral counseling, play therapy, potato race,
   primal therapy, prolonged, prolonged narcosis, protracted,
   psychodrama, psychological counseling, psychosurgery,
   psychosynthesis, psychotherapeutics, psychotherapy, race,
   radical therapy, rational-emotive therapy, reality therapy,
   recreational therapy, regatta, regression therapy, relay,
   relay race, release therapy, road race, run, sack race,
   scream therapy, sensitivity training, sensory awareness training,
   sleep treatment, speedway race, sprint, sprint race, spun-out,
   stock-car race, stretched-out, supportive therapy,
   three-legged race, torch race, track race, training group,
   transactional analysis, transcendental meditation,
   transpersonal therapy, vocational therapy, walk, yacht race



U.S. Gazetteer Counties (2000):

Marathon -- U.S. County in Wisconsin
   Population (2000):    125834
   Housing Units (2000): 50360
   Land area (2000):     1544.961790 sq. miles (4001.432497 sq. km)
   Water area (2000):    31.179336 sq. miles (80.754105 sq. km)
   Total area (2000):    1576.141126 sq. miles (4082.186602 sq. km)
   Located within:       Wisconsin (WI), FIPS 55
   Location:             44.900795 N, 89.738490 W
   Headwords:
    Marathon
    Marathon, WI
    Marathon County
    Marathon County, WI