Pronunciation: (un-rē'zu-nu-bul, -rēz'nu-),[key] —adj. 1. not reasonable or rational; acting at variance with or contrary to reason; not guided by reason or sound judgment; irrational: an unreasonable person. 2. not in accordance with practical realities, as attitude or behavior; inappropriate: His Bohemianism was an unreasonable way of life for one so rich. 3. excessive, immoderate, or exorbitant; unconscionable: an unreasonable price; unreasonable demands. 4. not having the faculty of reason.