An event characteristic of persons forming groups(noun)
WordNet. Princeton University. 2010.
Use "social event" in a sentence
"Marisa Louie, the curator of the Chinese Historical Society of America’s recent “Miss Chinatown U.S.A.” exhibit, told Asian Week magazine in March 2007 that the pageant was once “the social event in Chinatown.”"
"In the very front of her box, one of the largest and most prominent in the hall, Mrs. Andrew W. Carmody was staring ahead at the great flaming gas letters — CHARITY — 1882 — that said this was the greatest social event of the year."