The Collaborative International Dictionary of English v.0.48:

Regatta \Re*gat"ta\ (r?*g?t"t?), n.; pl. Regattas (-t?z). [It.
   regatta, regata.]
   Originally, a gondola race in Venice; now, a rowing or
   sailing race, or a series of such races.
   [1913 Webster]

WordNet (r) 3.0 (2006):

regatta
    n 1: a meeting for boat races

Moby Thesaurus II by Grady Ward, 1.0:

50 Moby Thesaurus words for "regatta":
   Highland games, Le Mans, Olympiad, Olympic games, air race,
   automobile race, bicycle race, boat race, carousel,
   contest of speed, cross-country race, dash, derby, dog race,
   drag race, endurance race, field day, footrace, games, gymkhana,
   heat, hurdle race, lap, marathon, marathon race, match race, meet,
   motorcycle race, obstacle race, potato race, race, rally, relay,
   relay race, road race, run, sack race, speedway race, sprint,
   sprint race, stock-car race, the Olympics, three-legged race,
   torch race, tournament, tourney, track meet, track race, walk,
   yacht race