/ Dictionary / Index T treasonous: Meaning and Definition of Find definitions for: trea•son•ous Pronunciation: (trē'zu-nus), [key] — adj. treasonable. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: treasonous (Thesaurus) treasonable treasr. Related Content Daily Word Quiz: rustic Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language