Definition of "ragwort" [rag•wort]

• Any of several plants of the very large genus Senecio in the composite family, having yellow flower heads, especially S. aureus of eastern North America. S. jacobaea, a European species poisonous to livestock, is widely naturalized in North America. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "I thought that she might have had ingested ragwort, which is extremely poisonous, often fatal for horses."
• "If the ragwort is a long way from grazing livestock (for example in the middle of woodland) then it does not need to be reported to the survey."
• "While it may not win the fight against ragwort on its 'own, it still has a part to play when used with other ragwort control agents such as ragwort flea beetle and ragwort plume moth."