Source : Webster's Revised Unabridged Dictionary (1913)

Pentathlon \Pen*tath"lon\, n.
   In the modern Olympic Games, a composite contest made up of a
   running broad jump, throwing the javelin, a 200-meter run,
   throwing the discus, and a 1500-meter run.

Pentathlon \Pen*tath"lon\, n. [NL., fr. Gr. ?; ? five + ? a
   contest.] (Gr. Antiq.)
   A fivefold athletic performance peculiar to the great
   national games of the Greeks, including leaping, foot racing,
   wrestling, throwing the discus, and throwing the spear.

Source : WordNet®

pentathlon
     n : an athletic contest consisting of five different events