naltostratusa stratus cloud at an intermediate altitude of 2 or 3 miles
Webster's Revised Unabridged Dictionary
naltostratus(Meteor) A cloud formation similar to cirro-stratus, but heavier and at a lower level; a stratus cloud at an intermediate altitude of 2 or 3 miles.
Century Dictionary and Cyclopedia
naltostratusA thin horizontal sheet of clouds, usually disappearing slowly: apparently a lower layer of what under favorable circumstances might have been a cumulus cloud. The outer surface, melting away at sunset, gives rise to beautiful sunset cloud-colors by reflection of light from the sun or the sky beyond the western horizon.
naltostratusA rather high cloud covering the sky as a layer whose lower surface is horizontal. The extreme boundaries of such an alto-stratus cloud thin away into a series of alto-cumuli.