The Collaborative International Dictionary of English v.0.48:

Emetic \E*met"ic\, a. [L. emeticus, Gr. ?, fr. ? to vomit, akin
   to L. vomere: cf. F. ['e]m['e]tique. See Vomit.] (Med.)
   Inducing to vomit; exciting the stomach to discharge its
   contents by the mouth. -- n. A medicine which causes
   vomiting.
   [1913 Webster]

WordNet (r) 3.0 (2006):

emetic
    n 1: a medicine that induces nausea and vomiting [syn: emetic,
         vomit, vomitive, nauseant]