The Collaborative International Dictionary of English v.0.48:

Casino \Ca*si"no\, n.; pl. E. Casinos, It. Casini. [It.
   casino, dim. of casa house, fr. L. casa cottage. Cf.
   Cassing.]
   1. A small country house.
      [1913 Webster]

   2. A building or room used for meetings, or public
      amusements, for dancing, etc., sometimes having gambling
      tables or devices.
      [1913 Webster +PJC]

   3. A game at cards. See Cassino.
      [1913 Webster]

   4. a business establishment for which the primary business is
      gambling, having various types of gambling tables, such as
      blackjack or roulette, and usually also slot machines, and
      sometimes other forms of gambling, such as poker; also,
      the main room of such an establishment where the gambling
      is conducted; as, the Trump casinos in Atlantic City.
      [PJC]

WordNet (r) 3.0 (2006):

casino
    n 1: a public building for gambling and entertainment [syn:
         casino, gambling casino]
    2: a card game in which cards face up on the table are taken
       with eligible cards in the hand [syn: casino, cassino]

Moby Thesaurus II by Grady Ward, 1.0:

48 Moby Thesaurus words for "casino":
   amusement park, ballroom, baths, betting house, betting parlor,
   cabaret, cafe chantant, cafe dansant, club, clubhouse, crib,
   dance floor, dance hall, dancery, dancing pavilion,
   entertainment industry, flat, fun-fair, gambling den,
   gambling hall, gambling hell, gambling house, gaming house,
   gathering place, hangout, haunt, health resort, hell, joint,
   juke joint, meeting place, night spot, nightclub, nitery, poolroom,
   purlieu, rallying point, resort, roadhouse, show biz,
   show business, spa, sporting house, springs, stamping ground,
   tavern, theater, watering place