bit·ter·weed /ˈbɪtɚ/
  Bit·ter·weed n. Bot. A species of Ambrosia (Ambrosia artemisiæfolia); Roman worm wood.
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  bitterweed
       n 1: widespread European weed with spiny tongue-shaped leaves and
            yellow flowers; naturalized in United States [syn: oxtongue,
             bristly oxtongue, bugloss, Picris echioides]
       2: any of numerous chiefly North American weedy plants
          constituting the genus Ambrosia that produce highly
          allergenic pollen responsible for much hay fever and
          asthma [syn: ragweed, ambrosia]