The Collaborative International Dictionary of English v.0.48:

Hausen \Hau"sen\ (h[add]"s[e^]n), n. [G.] (Zool.)
   A large sturgeon (Acipenser huso syn. Huso huso) from the
   region of the Black Sea; also called Beluga. It is
   sometimes twelve feet long, and provides the highest quality
   caviar.
   [1913 Webster +PJC]

The Collaborative International Dictionary of English v.0.48:

Beluga \Be*lu"ga\ (b[-e]*l[=u]"g[.a]), n. [Russ. bieluga a sort
   of large sturgeon, prop. white fish, fr. bieluii white. The
   whale is now commonly called bieluka in Russian.]
   1. (Zool.) A cetacean allied to the dolphins.
      [1913 Webster]

   Note: The northern beluga (Delphinapterus catodon) is the
         white whale and white fish of the whalers. It grows
         to be from twelve to eighteen feet long.
         [1913 Webster]

   2. the sturgeon (Huso huso) native to the Black Sea and
      Caspian Sea; -- also called hausen. It is valued for its
      roe, sold as caviar, and is also used for production of
      isinglass. See also sturgeon.
      [PJC]

   3. the caviar obtained from the beluga[2]; -- also called
      beluga caviar. The caviar of the beluga is considered
      the finest sort, larger and of a taste superior to that
      obtained from other sturgeon. See also sturgeon and
      caviar.
      [PJC]

The Collaborative International Dictionary of English v.0.48:

Caviar \Cav"i*ar\, Caviare \Ca*viare"\, n. [F. caviar, fr. It.
   caviale, fr. Turk. Hav[imac][=a]r.]
   The roes of the sturgeon, prepared and salted; -- used as a
   relish, esp. in Russia.
   [1913 Webster]

   Note: Caviare was considered a delicacy, by some, in
         Shakespeare's time, but was not relished by most. Hence
         Hamlet says of a certain play. "'T was caviare to the
         general," i. e., above the taste of the common people.
         [1913 Webster]

WordNet (r) 3.0 (2006):

caviar
    n 1: salted roe of sturgeon or other large fish; usually served
         as an hors d'oeuvre [syn: caviar, caviare]

Moby Thesaurus II by Grady Ward, 1.0:

22 Moby Thesaurus words for "caviar":
   albumen, anguille, eel, egg, egg white, eggshell, fish, fish eggs,
   glair, kipper, kippered salmon, ovule, poisson, red herring, roe,
   seafood, smoked herring, spawn, vitellus, white, yellow, yolk