/ Dictionary / Index U unreason: Meaning and Definition of Find definitions for: un•rea•son Pronunciation: (un-rē'zun), [key] — n. inability or unwillingness to think or act rationally, reasonably, or sensibly; irrationality. lack of reason or sanity; madness; confusion; disorder; chaos: a world torn by unreason. —v.t. to upset or disrupt the reason or sanity of: The devious plot soon unreasoned the general. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: unreason (Thesaurus) unrealized unreasonable Related Content Daily Word Quiz: careening Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language