The Collaborative International Dictionary of English v.0.48:

Cow parsley \Cow" pars`ley\ (kou` p?rs`l?). (Bot.)
   An umbelliferous plant of the genus Ch[ae]rophyllum
   (Ch[ae]rophyllum temulum and Ch[ae]rophyllum sylvestre).
   [1913 Webster]

WordNet (r) 3.0 (2006):

cow parsley
    n 1: coarse erect biennial Old World herb introduced as a weed
         in eastern North America [syn: cow parsley, wild
         chervil, Anthriscus sylvestris]