Canada thistle
A close up of the Canada thistle.
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a prickly European weed (Cirsium arvense) of the composite family, with heads of purplish flowers and wavy leaves: now common as a fast-spreading, injurious weed throughout the N U.S.
Used by arrangement with John Wiley & Sons, Inc.
noun
The American Heritage® Dictionary of the English Language, 4th edition Copyright © 2010 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
A perennial herb (Cirsium arvense) in the composite family, native to Europe and naturalized as a noxious weed in North America, having spiny-margined leaves and rose-purple or sometimes white flower heads.