the noise which accompanies or follows a flash of lightning, due to the disturbance of air by a discharge of electricity (see LIGHTNING; ATMOSPHERIC ELECTRICITY and METEOROLOGY). The Old English word is bunor, also the name of the Scandinavian god Thor, which is cognate with Dutch donder, German Donner. The root is than,- Indo-European tan-, cf. Latin tonare, tonitru. This root is apparently another form of stan-, as in Skr. .stare, to sound, thunder, Gr. to groan, Eng. "stun."