The Collaborative International Dictionary of English v.0.48:

Sulks \Sulks\, n. pl.
   The condition of being sulky; a sulky mood or humor; as, to
   be in the sulks.
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

59 Moby Thesaurus words for "sulks":
   antipathy, averseness, aversion, backwardness, blahs, blue devils,
   blues, cursoriness, disagreement, disinclination, dismals,
   disobedience, disrelish, dissent, distaste, dods, doldrums,
   dolefuls, dorts, dumps, foot-dragging, fractiousness, frumps,
   grudging consent, grudgingness, grumps, indisposedness,
   indisposition, indocility, intractableness, lack of enthusiasm,
   lack of zeal, megrims, mopes, mulligrubs, mumps, mutinousness,
   nolition, obstinacy, opposition, perfunctoriness, pouts,
   recalcitrance, recalcitrancy, refractoriness, refusal, reluctance,
   renitence, renitency, repugnance, resistance, slowness,
   stubbornness, sulk, sulkiness, sullenness, sullens, unenthusiasm,
   unwillingness