noun (n)

• widespread European weed having yellow daisylike flowers; sometimes an obnoxious weed and toxic to cattle if consumed in quantity(noun.plant)

  Synonym:
  benweed, ragwort, senecio jacobaea, tansy ragwort
  

  source: wordnet30
• any of numerous chiefly North American weedy plants constituting the genus Ambrosia that produce highly allergenic pollen responsible for much hay fever and asthma(noun.plant)

  Synonym:
  ambrosia, bitterweed
  

  source: wordnet30
• A common American composite weed (Ambrosia artemisiæfolia) with finely divided leaves; hogweed.(noun)

  source: webster1913