supernumerary rainbow
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supernumerary rainbow
[¦sü·pər′nü·mə‚rer·ē ′rān‚bō] (optics)
One of a set of weakly colored rainbow arcs sometimes discernible inside a primary rainbow; they are of smaller angular width, and fade toward the common center.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.