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.
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.