not reasonable or rational; acting at variance with or contrary to reason; not guided by reason or sound judgment; irrational

an unreasonable person.

not in accordance with practical realities, as attitude or behavior; inappropriate

His Bohemianism was an unreasonable way of life for one so rich.

excessive, immoderate, or exorbitant; unconscionable

an unreasonable price; unreasonable demands.

not having the faculty of reason.

adjective

logical , practical , pragmatic , realistic , reasonable , sensible , cheap , economical , low , plain

adjective

absurd , all wet , arbitrary , biased , capricious , contradictory , erratic , fallacious , far-fetched , foolish , full of hot air , headstrong , illogical , incoherent , incongruous , inconsequential , inconsistent , invalid , irrational , loose , mad , nonsensical , off the wall , opinionated , preposterous , quirky , reasonless , senseless , silly , stupid , thoughtless , unreasoned , vacant , wrong , absonant , costing an arm and a leg , dear , excessive , exorbitant , extortionate , extreme , far-out * , illegitimate , immoderate , improper , inordinate , intemperate , out of bounds , overkill * , overmuch , peremptory , posh , pricey , steep * , stiff * , too great , too much , too-too , uncalled-for * , unconscionable , undue , unfair , unjust , unjustifiable , unlawful , unrightful , unwarrantable , unwarranted , up to here , way out , wrongful , obscene , ridiculous , shocking , extravagant , fanatical , fatuous , impractical , inappropriate , inflexible , obstinate , paralogical , paralogistic , stubborn , unwise