noun. a stratus cloud at an intermediate altitude of 2 or 3 miles.
1. Noun, singular or mass Such cold-front cumuli often pile up right along the frontal boundary on comparatively short notice, whereas the cirrus, cirrostratus, altostratus, stratus and nimbostratus of a warm front often are clouds that cover a large area. 2. Adjective Mid-level clouds are designated with a prefix of “alto-” and include altocumulus and altostratus clouds.