noun
nimbostratus
A thick, dark, low-level cloud that brings continuous rain or snow. Technical term used in meteorology.
乱層雲は雨や雪を長時間降らせる雲です。
Nimbostratus is a cloud that brings rain or snow for long periods.
Compound of 乱 (ran, 'disorderly') + 層 (sō, 'layer') + 雲 (un, 'cloud'), reflecting its thick, layered, and often ragged appearance.