Definition of altostratus in US English:



  • Cloud forming a continuous uniform layer that resembles stratus but occurs at medium altitude, usually 6,500–23,000 feet (2–7 km).

    • ‘The grey layer looks like and should be an altostratus although the fronts look different in the tropical regions.’
    • ‘Where enough light shows through cirrostratus clouds to create shadows, it does not with altostratus.’
    • ‘An altostratus cloud usually covers the whole sky and has a gray or blue-gray appearance.’
    • ‘You were probably looking at the sun or moon through a layer of altostratus clouds.’
    • ‘From the ground this altostratus looks white or slightly blue and watery.’


Late 19th century: from modern Latin alto- (from Latin altus ‘high’) + stratus.