The Collaborative International Dictionary of English v.0.48:

Fretful \Fret"ful\, a. [See 2d Fret.]
   Disposed to fret; ill-humored; peevish; angry; in a state of
   vexation; as, a fretful temper. -- Fret"ful*ly, adv. --
   Fret"ful*ness, n.

   Syn: Peevish; ill-humored; ill-natured; irritable; waspish;
        captious; petulant; splenetic; spleeny; passionate;
        angry.

   Usage: Fretful, Peevish, Cross. These words all
          indicate an unamiable working and expression of
          temper. Peevish marks more especially the inward
          spirit: a peevish man is always ready to find fault.
          Fretful points rather to the outward act, and marks a
          complaining impatience: sickly children are apt to be
          fretful. Crossness is peevishness mingled with
          vexation or anger.
          [1913 Webster]

WordNet (r) 3.0 (2006):

fretfully
    adv 1: in a fretful manner; "fretfully, the baby tossed in his
           crib"