Source : Webster's Revised Unabridged Dictionary (1913)

Sullen \Sul"len\, a. [OE. solein, solain, lonely, sullen;
   through Old French fr. (assumed) LL. solanus solitary, fr. L.
   solus alone. See {Sole}, a.]
   1. Lonely; solitary; desolate. [Obs.] --Wyclif (Job iii. 14).

   2. Gloomy; dismal; foreboding. --Milton.

            Solemn hymns so sullen dirges change. --Shak.

   3. Mischievous; malignant; unpropitious.

            Such sullen planets at my birth did shine. --Dryden.

   4. Gloomily angry and silent; cross; sour; affected with ill
      humor; morose.

            And sullen I forsook the imperfect feast. --Prior.

   5. Obstinate; intractable.

            Things are as sullen as we are.       --Tillotson.

   6. Heavy; dull; sluggish. ``The larger stream was placid, and
      even sullen, in its course.'' --Sir W. Scott.

   Syn: Sulky; sour; cross; ill-natured; morose; peevish;
        fretful; ill-humored; petulant; gloomy; malign;
        intractable.

   Usage: {Sullen}, {Sulky}. Both sullen and sulky show
          themselves in the demeanor. Sullenness seems to be an
          habitual sulkiness, and sulkiness a temporary
          sullenness. The former may be an innate disposition;
          the latter, a disposition occasioned by recent injury.
          Thus we are in a sullen mood, and in a sulky fit.

                No cheerful breeze this sullen region knows; The
                dreaded east is all the wind that blows. --Pope.
          -- {Sul"len*ly}, adv. -- {Sul"len*ness}, n.

Source : WordNet®

sullenness
     n 1: a gloomy ill-tempered feeling [syn: {moroseness}, {glumness}]
     2: a sullen moody resentful disposition [syn: {sulkiness}, {moroseness},
         {sourness}]