The Collaborative International Dictionary of English v.0.48:

Kava \Ka"va\, n. [Polynesian.] (Bot.)
   A species of Macropiper (Macropiper methysticum), the
   long pepper, from the root of which an intoxicating beverage
   is made by the Polynesians, by a process of mastication;
   also, the beverage itself. [Written also kawa, kava, and
   ava.]
   [1913 Webster]