noun, plural nim·bo·stra·tus.
- a cloud of a class characterized by a formless layer that is almost uniformly dark gray; a rain cloud of the layer type, of low altitude, usually below 8000 feet (2440 meters).
noun plural -ti (-taɪ)
- a dark-coloured rain-bearing stratus cloud
Plural nimbostrati (nĭm′bō-străt′ī′)
- A dark, gray, mid-altitude cloud that often covers the entire sky and precipitates rain, snow, or sleet. Nimbostratus clouds generally form around 2,000 m (6,560 ft) but often extend to much higher and lower altitudes. See illustration at cloud.