The Collaborative International Dictionary of English v.0.48:

Curare \Cu*ra"re\ Curari \Cu*ra"ri\(k?-r?"r?), n. [Native name.
   Cf. Wourall.]
   A black resinoid extract prepared by the South American
   Indians from the bark of several species of Strychnos
   (Strychnos toxifera, etc.). It sometimes has little effect
   when taken internally, but is quickly fatal when introduced
   into the blood, and used by the Indians as an arrow poison.
   [Written also urari, woorali, woorari, etc.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

curare
    n 1: a toxic alkaloid found in certain tropical South American
         trees that is a powerful relaxant for striated muscles;
         "curare acts by blocking cholinergic transmission at the
         myoneural junction" [syn: tubocurarine, curare]