Source : Webster's Revised Unabridged Dictionary (1913)

Unacceptable \Un`ac*cept"a*ble\, a.
   Not acceptable; not pleasing; not welcome; unpleasant;
   disagreeable; displeasing; offensive. --
   {Un`ac*cept"a*ble*ness}, n. -- {Un`ac*cept"a*bly}, adv.

Source : WordNet®

unacceptably
     adv : to an unacceptable degree; "The percentage of lead in our
           drinking water is unacceptably high" [syn: {intolerably}]
           [ant: {acceptably}, {acceptably}]