The Collaborative International Dictionary of English v.0.48:

nightclub \nightclub\ n.
   An establishment providing entertainment (as singers,
   dancers, or comedy acts), usually open late into the night or
   early morning, typically serving alcoholic beverages and
   food.

   Syn: cabaret.
        [WordNet 1.5 +PJC]

WordNet (r) 3.0 (2006):

nightclub
    n 1: a spot that is open late at night and that provides
         entertainment (as singers or dancers) as well as dancing
         and food and drink; "don't expect a good meal at a
         cabaret"; "the gossip columnist got his information by
         visiting nightclubs every night"; "he played the drums at a
         jazz club" [syn: cabaret, nightclub, night club,
         club, nightspot]

Moby Thesaurus II by Grady Ward, 1.0:

72 Moby Thesaurus words for "nightclub":
   Elizabethan theater, Globe Theatre, Greek theater, alehouse,
   amphitheater, amusement park, arena theater, auditorium, ballroom,
   bar, barrel house, barroom, beer garden, beer parlor, bistro,
   blind tiger, cabaret, cafe, cafe chantant, cafe dansant, casino,
   circle theater, club, cocktail lounge, concert hall, dance floor,
   dance hall, dancing pavilion, discotheque, dive, dramshop,
   drinking saloon, entertainment industry, fun-fair, gin mill,
   groggery, grogshop, hall, honky-tonk, house, juke joint,
   little theater, local, music hall, night spot, nitery, opera,
   opera house, outdoor theater, playhouse, pothouse, pub, public,
   public house, rathskeller, resort, roadhouse, rumshop, saloon,
   saloon bar, show biz, show business, showboat, speakeasy,
   supper club, taproom, tavern, theater, theater-in-the-round,
   theatron, watering place, wine shop