Source : Webster's Revised Unabridged Dictionary (1913)

Resentful \Re*sent"ful\ (-f?l), a.
   Inclined to resent; easily provoked to anger; irritable. --
   {Re*sent"ful*ly}, adv.

Source : WordNet®

resentful
     adj : full of or marked by resentment or indignant ill will;
           "resentful at the way he was treated"; "a sullen
           resentful attitude" [ant: {unresentful}]