The Collaborative International Dictionary of English v.0.48:

Papaverine \Pa*pav"er*ine\, n. (Chem.)
   An alkaloid found in opium. It has a weaker therapeutic
   action than morphine.
   [1913 Webster]

WordNet (r) 3.0 (2006):

papaverine
    n 1: an alkaloid medicine (trade name Kavrin) obtained from
         opium; used to relax smooth muscles; it is nonaddictive
         [syn: papaverine, Kavrin]