The Collaborative International Dictionary of English v.0.48:

Glower \Glow"er\, v. i. [imp. & p. p. Glowered; p. pr. & vb.
   n. Glowering.] [Cf. Gloar.]
   to look intently; to stare angrily or with a scowl.
   --Thackeray.
   [1913 Webster]

WordNet (r) 3.0 (2006):

glower
    n 1: an angry stare [syn: glare, glower]
    v 1: look at with a fixed gaze; "The girl glared at the man who
         tried to make a pass at her" [syn: glower, glare]
    2: look angry or sullen, wrinkle one's forehead, as if to signal
       disapproval [syn: frown, glower, lour, lower]

Moby Thesaurus II by Grady Ward, 1.0:

46 Moby Thesaurus words for "glower":
   angry look, bedroom eyes, color, come-hither look, dirty look,
   evil eye, flush, frown, gape, gaze, glad eye, glare, gloom,
   glowering look, gnarl, goggle, grimace, growl, knit the brow,
   long face, look, look black, look daggers, look sullen, lower,
   make a lip, make a moue, malocchio, mantle, moue, mow, offense,
   ogle, penetrating look, pique, pout, redden, scowl, snap, snarl,
   spit, stare, umbrage, watch, whammy, wry face