Showing a brooding ill humor or silent resentment; morose or sulky.
Gloomy or somber in tone, color, or portent: sullen, gray skies.
Sluggish; slow: the sullen current of a canal.
[Middle English solein, from Anglo-Norman solein, alone, from sol, single, from Latin sōlus, by oneself alone; see s(w)e- in Indo-European roots.] sul'len·ly adv., sul'len·ness n.
(sŭl'ən) 