water hemlock

from WordNet (r) 3.0 (2006)

water hemlock
    n 1: tall erect highly poisonous Eurasiatic perennial herb
         locally abundant in marshy areas [syn: {water hemlock},
         {Cicuta verosa}]

from The Collaborative International Dictionary of English v.0.48

Water hemlock \Wa"ter hem"lock\ (Bot)
   (a) A poisonous umbelliferous plant ({Cicuta virosa}) of
       Europe; also, any one of several plants of that genus.
   (b) A poisonous plant ({[OE]nanthe crocata}) resembling the
       above.
       [1913 Webster]