A plant of the genus Urtica, covered with minute sharp
   hairs containing a poison that produces a stinging sensation. Urtica
   gracitis is common in the Northern, and U. chamaedryoides in the
   Southern, United States. the common European species, U. urens and U.
   dioica, are also found in the Eastern united States. U. pilulifera is
   the Roman nettle of England.