bitterweed

Noun

• any of numerous chiefly North American weedy plants constituting the genus Ambrosia that produce highly allergenic pollen responsible for much hay fever and asthma

• widespread European weed with spiny tongue-shaped leaves and yellow flowers; naturalized in United States

Related words

• Synonyms: 
  ragweed , ambrosia , oxtongue , bristly oxtongue , bugloss , Picris echioides