middle clouds[′mid·əl ′klau̇dz]
Types of clouds the mean level of which is between 6500 and 20,000 feet (1980 and 6100 meters); the principal clouds in this group are altocumulus and altostratus.
Clouds at medium heights—that is, which occur between 6000 (approximately 1.8 km) and 20,000 ft (6 km). The names are prefixed by the word alto, such as in altocumulus and altocirrus clouds. Also called middle clouds.