<p><strong>noun</strong></p><ul><li>A brilliant electric spark discharge in the atmosphere, occurring within a thundercloud, between clouds, or between a cloud and the ground.</li></ul><p><strong>verb (used without object)</strong></p><ul><li>to emit a flash or flashes of lightning (often used impersonally with it as subject): If it starts to lightning, we'd better go inside.</li></ul><p><strong>adjective</strong></p><ul><li>of, relating to, or resembling lightning, especially in regard to speed of movement: lightning speed.</li><li>lightning flashes; lightning speed.</li></ul>