The Collaborative International Dictionary of English v.0.48:

Shimmering \Shim"mer*ing\, n.
   A gleam or glimmering. "A little shimmering of a light."
   --Chaucer.
   [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]

Moby Thesaurus II by Grady Ward, 1.0:

37 Moby Thesaurus words for "shimmering":
   blink, blinking, blinky, coruscant, coruscating, coruscation,
   firefly, glimmer, glimmering, glimmerous, glimmery, glisten,
   glistening, glister, glistering, glitter, glittering, glittery,
   glowworm, scintilla, scintillant, scintillating, scintillation,
   scintillescent, shimmer, shimmery, spangle, spangly, spark,
   sparkle, sparkling, stroboscopic light, tinsel, tinselly, twinkle,
   twinkling, twinkly