the.com/sheetlightning

means Lightning seen as a broad, diffuse flash that illuminates a cloud or the sky without a visible bolt, usually because the actual stroke is hidden behind clouds or too far away to hear the thunder.

from A plain English compound of "sheet" and "lightning," named for the way the flash spreads across the sky like a sheet of cloth or paper rather than striking as a jagged line. "Sheet" comes from Old English "sciete," a piece of cloth, ultimately from a root meaning to shoot or project outward — fittingly, since the light seems flung across the whole cloud. The term is descriptive rather than scientific: meteorologists note it isn't a separate kind of lightning at all, just an ordinary discharge whose bolt is veiled from view.