The Collaborative International Dictionary of English v.0.48:

Rabbit \Rab"bit\ (r[a^]b"b[i^]t), n. [OE. rabet, akin to OD.
   robbe, robbeken.] (Zool.)
   Any of the smaller species of the genus Lepus, especially the
   common European species (Lepus cuniculus), which is often
   kept as a pet, and has been introduced into many countries.
   It is remarkably prolific, and has become a pest in some
   parts of Australia and New Zealand.
   [1913 Webster]

   Note: The common American rabbit (Lepus sylvatica) is
         similar but smaller. See Cottontail, and Jack
         rabbit, under 2d Jack. The larger species of Lepus
         are commonly called hares. See Hare.
         [1913 Webster]

   Angora rabbit (Zool.), a variety of the domestic rabbit
      having long, soft fur.

   Rabbit burrow, a hole in the earth made by rabbits for
      shelter and habitation.

   Rabbit fish. (Zool.)
   (a) The northern chimaera (Chimaera monstrosa).
   (b) Any one of several species of plectognath fishes, as the
       bur fish, and puffer. The term is also locally applied to
       other fishes.

   Rabbits' ears. (Bot.) See Cyclamen.

   Rabbit warren, a piece of ground appropriated to the
      breeding and preservation of rabbits. --Wright.

   Rock rabbit.
   (a) (Zool.) See Daman, and Klipdas.
   (b) the pika.

   Welsh rabbit, a dish of which the chief constituents are
      melted cheese over toasted bread, flavored in various
      ways, as with ale, beer, milk, or spices. The name is
      popularly said to be a corruption of Welsh rare bit, but
      it is probably merely a humorous designation; -- also
      called Welsh rarebit.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Welsh rarebit \Welsh rarebit\, n.
   same as Welsh rabbit.
   [PJC]

WordNet (r) 3.0 (2006):

Welsh rarebit
    n 1: cheese melted with ale or beer served over toast [syn:
         Welsh rarebit, Welsh rabbit, rarebit]