The Collaborative International Dictionary of English v.0.48:

Athletics \Ath*let"ics\, n.
   The art of training by athletic exercises; the games and
   sports of athletes.
   [1913 Webster]

WordNet (r) 3.0 (2006):

athletics
    n 1: an active diversion requiring physical exertion and
         competition [syn: sport, athletics]
    2: a contest between athletes [syn: athletic contest,
       athletic competition, athletics]
    3: participation in sports events as an extracurricular activity

Moby Thesaurus II by Grady Ward, 1.0:

35 Moby Thesaurus words for "athletics":
   Rugby, acrobatics, agonistics, amusement, association football,
   bathing, breather, calisthenics, diversion, drill, entertainment,
   exercise, exercising, games, gymnastic exercises, gymnastics,
   isometrics, natation, palaestra, pastime, physical education,
   physical jerks, practice, recreation, rugger, setting-up exercises,
   soccer, sports, stretch, swimming, track, track and field,
   tumbling, workout, yoga