Pronunciation: (al"tō-kyOO'myu-lus), [key]
—pl. -lus. Meteorol.
a cloud of a class characterized by globular masses or rolls in layers or patches, the individual elements being larger and darker than those of cirrocumulus and smaller than those of stratocumulus: of medium altitude, about 8000–20,000 ft. (2450–6100 m).
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.