1. Any of numerous often weedy plants of several genera of the composite family, including Cirsium, Carduus, and Onopordum, having prickly leaves and floral bracts.
2. Any of various other prickly plants, such as Russian thistle.
[Middle English, fromOld Englishthistel; see steig- in the Appendix of Indo-European roots.]
(click for a larger image)thistle
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
The American Heritage Dictionary Blog
Check out our blog, updated regularly, for new words and revised definitions, interesting images from the 5th edition, discussions of usage, and more.