The Collaborative International Dictionary of English v.0.48:

Sulky \Sulk"y\, a. [Compar. Sulkier; superl. Sulkiest.] [See
   Sulkiness, and cf. Sulky, n.]
   Moodly silent; sullen; sour; obstinate; morose; splenetic.
   [1913 Webster]

   Syn: See Sullen.
        [1913 Webster]