Source : Webster's Revised Unabridged Dictionary (1913)

Unreasonable \Un*rea"son*a*ble\, a.
   Not reasonable; irrational; immoderate; exorbitant. --
   {Un*rea"son*a*ble*ness}, n. -- {Un*rea"son*a*bly}, adv.

Source : WordNet®

unreasonable
     adj 1: not reasonable; not showing good judgment [ant: {reasonable}]
     2: pungent adjectives of disesteem; "gave me a cockamamie
        reason for not going"; "wore a goofy hat"; "a silly idea";
        "some wacky plan for selling more books" [syn: {cockamamie},
         {cockamamy}, {goofy}, {sappy}, {silly}, {wacky}, {whacky},
         {zany}]
     3: absurd and inappropriate; "the unreasonable nimbus of
        romance with which she had encircled that man"- Thomas
        Hardy
     4: beyond normal limits; "excessive charges"; "a book of
        inordinate length"; "his dress stops just short of undue
        elegance"; "unreasonable demands" [syn: {excessive}, {inordinate},
         {undue}]
     5: inconsistent with reason or logic or common sense; "the
        absurd predicament of seeming to argue that virtue is
        highly desirable but intensely unpleasant"- Walter Lippman
        [syn: {absurd}]