The Collaborative International Dictionary of English v.0.48:

Olympic games \O*lym"pic games\, or Olympian games \O*lym"pi*an
games\ . (Greek Antiq.),
   The greatest of the national festivals of the ancient Greeks,
   consisting of athletic games and races, dedicated to Olympian
   Zeus, celebrated once in four years at Olympia, and
   continuing five days.
   [1913 Webster] Olympic games

The Collaborative International Dictionary of English v.0.48:

Olympic games \O*lym"pic games\, or Olympics \O*lym"pics\
   A modified revival of the ancient Olympian games, consisting
   of international athletic games, races, etc., now held once
   in four years, the first having been at Athens in 1896.

   Note: There are now two sets of modern Olympic games, the
         summer games and the winter games. Both had been held
         every four years, in the same year, but in 1998 for the
         first time the winter games began to be held two years
         after the summer games, though each series is still
         held only once every four years. The number and types
         of sports contests held at the olympics has greatly
         expanded from the original number.
         [Webster 1913 Suppl. +PJC]

WordNet (r) 3.0 (2006):

Olympic Games
    n 1: the modern revival of the ancient games held once every 4
         years in a selected country [syn: Olympic Games,
         Olympics, Olympiad]
    2: the ancient Panhellenic celebration at Olympia in honor of
       Zeus; held every 4 years beginning in 776 BC [syn: Olympian
       Games, Olympic Games]