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,

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.

"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.]

For further exploring for "olympic games" in Webster Dictionary Online