The Collaborative International Dictionary of English v.0.48:

Shimmer \Shim"mer\, n.
   A faint, tremulous light; a gleaming; a glimmer.
   [1913 Webster]

         TWo silver lamps, fed with perfumed oil, diffused . . .
         a trembling twilight-seeming shimmer through the quiet
         apartment.                               --Sir W.
                                                  Scott.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Shimmer \Shim"mer\, v. i. [imp. & p. p. Shimmered; p. pr. &
   vb. n. Shimmering.] [OE. schimeren, AS. scimerian; akin to
   sc[imac]mian, sc[imac]man, to glitter, D. schemeren, G.
   schimmern, Dan. skimre, Sw. skimra, AS. sc[imac]ma a light,
   brightness, Icel. sk[imac]ma, Goth. skeima a torch, a
   lantern, and E. shine. [root]157. See Shine, v. i.]
   To shine with a tremulous or intermittent light; to shine
   faintly; to gleam; to glisten; to glimmer.
   [1913 Webster]

         The shimmering glimpses of a stream.     --Tennyson.
   [1913 Webster]

WordNet (r) 3.0 (2006):

shimmer
    n 1: a weak and tremulous light; "the shimmer of colors on
         iridescent feathers"; "the play of light on the water"
         [syn: shimmer, play]
    v 1: shine with a weak or fitful light; "Beech leaves shimmered
         in the moonlight"
    2: give off a shimmering reflection, as of silk

Moby Thesaurus II by Grady Ward, 1.0:

33 Moby Thesaurus words for "shimmer":
   blink, blinking, coruscate, coruscation, firefly, flicker, gleam,
   glimmer, glimmering, glint, glisk, glisten, glister, glitter,
   glittering, gloss, glow, glowworm, light, ripple, scintilla,
   scintillate, scintillation, shimmering, shine, spangle, spark,
   sparking, sparkle, stroboscopic light, tinsel, twinkle,
   twinkling