Entry 2 senses Webster, 1913 Water gall /wôt'-ẽr gôl/ · Wa·ter gall · IPA 01 A cavity made in the earth by a torrent of water; a washout. 1. A cavity made in the earth by a torrent of water; a washout. 2. A watery appearance in the sky, accompanying the rainbow; a secondary or broken rainbow. “These water galls, in her dim element, Foretell new storms to those already spent.” — Shak. “False good news are [is] always produced by true good, like the water gall by the rainbow.” — Walpole.