/al'toh stray"teuhs, -strat"euhs/ , n. , pl. altostratus . Meteorol.
a cloud of a class characterized by a generally uniform gray sheet or layer, lighter in color than nimbostratus and darker than cirrostratus: of medium altitude, about 8000-20,000 ft. (2450-6100 m).
[ 1890-95; ALTO- + STRATUS ]