Source : Webster's Revised Unabridged Dictionary (1913)

Unsufferable \Un*suf"fer*a*ble\, a.
   Insufferable. [Obs.] --Hooker. -- {Un*suf"fer*a*bly}, adv.
   [Obs.]

Source : WordNet®

unsufferable
     adj : used of persons or their behavior; "impossible behavior";
           "insufferable insolence" [syn: {impossible}, {insufferable},
            {unacceptable}]