1.  olympiad(n = noun.time) - one of the four-year intervals between Olympic Games; used to reckon time in ancient Greece for twelve centuries beginning in 776 BC;
is a kind of period, period of time, time period

2.  olympiad(n = noun.event) olympic games, olympics - the modern revival of the ancient games held once every 4 years in a selected country;
is a kind of athletic competition, athletic contest, athletics
has particulars: winter olympic games, winter olympics

1.  A period of four years, by which the ancient Greeks reckoned time, being the interval from one celebration of the Olympic games to another, beginning with the victory of Corb. c.; as, the era of the olympiads. [1913 Webster]

2.  The quadrennial celebration of the modern Olympic games; as, the first Olympiad (1906). See Olympics. [Webster 1913 Suppl.]

olympiad, n.
1 a a period of four years between Olympic games, used by the ancient Greeks in dating events. b a four-yearly celebration of the ancient Olympic Games.
2 a celebration of the modern Olympic Games.
3 a regular international contest in chess etc.

Etymology:
ME f. F Olympiade f. L Olympias Olympiad- f. Gk Olumpias Olumpiad- f. Olumpios: see OLYMPIAN, OLYMPIC