Source : Webster's Revised Unabridged Dictionary (1913)

Unpleasant \Un*pleas"ant\, a.
   Not pleasant; not amiable or agreeable; displeasing;
   offensive. -- {Un*pleas"ant*ly}, adv. -- {Un*pleas"ant*ness},
   n.

Source : WordNet®

unpleasantly
     adv : in an unpleasant manner; "he had been unpleasantly
           surprised" [ant: {pleasantly}]