An instrument that indicates the altitude of an object above a fixed level.
Pressure altimeters use an aneroid barometer with a scale graduated in altitude instead of pressure.
A middle cloud, usually white or gray. Often occurs in layers or patches with wavy, rounded masses or rolls. A middle cloud composed of gray or bluish sheets or layers of uniform appearance. In the thinner regions, the sun or moon appears dimly visible. An instrument designed to measure wind speed.