- The definition of a triathlon is a race where three different sporting events are done.
A race involving running, swimming and biking is an example of a triathlon.
triathlon definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
an endurance race combining three consecutive events (swimming, bicycling, and running)
Origin: tri- plush Classical Greek athlon, a contest
triathlon definition by American Heritage Dictionary
An athletic contest in which participants compete without stopping in three successive events, usually long-distance swimming, bicycling, and running.
Origin: tri- + (dec)athlon.