Meaning

noun an appearance of reflected light

noun a flash of light (especially reflected light)

verb be shiny, as if wet

originA variant of Middle English gleimen, gleym (“to smear; to make slimy or sticky; to fill up (the stomach); to nauseate; of a slimy or viscous substance: to be stuck together; (figuratively) to captivate, ensnare; to infect with heresy”) [and other forms], probably a blend of glet (“slimy or viscous matter produced by animals; mucus, phlegm; congestion of mucus or phlegm in the body; viscosity”),…

Etymology from Wiktionary, CC BY-SA 3.0