/ Dictionary / Index T thistle: Meaning and Definition of Find definitions for: this•tle Pronunciation: (this'ul), [key] — n. any of various prickly, composite plants having showy, purple flower heads, esp. of the genera Cirsium, Carduus, or Onopordum. any of various other prickly plants. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: thistle (Thesaurus) Thisbe thistle butterfly Related Content Daily Word Quiz: eureka Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language