shim·mer (shĭmʹər)intr.v. shim·mered, shim·mer·ing, shim·mers 1. To shine with a subdued flickering light. See Synonyms at flash. 2. To appear as a wavering or flickering image, as in a reflection on water or through heat waves in air.n. A flickering or tremulous light; a glimmer. [Middle English shimeren, from Old English scimerian.] shimʹmer·ing·ly adv.shimʹmer·y adj.