nimbus
It is called a nimbus cloud or if you are describing it just call it a threatning cloud
cumulus cloud
The type of cloud that produces thunderstorms is called a cumulonimbus cloud. These clouds are large, towering clouds that can reach high altitudes and are associated with heavy rainfall, thunder, lightning, and sometimes hail.
Stratus
A "Nimbus Cloud" is a cloud that produces precipitation. Most likely a Hail or Snow Cloud.
Any cloud, including clumlus.
Precipitation occurs when evaporation forms clouds and the clouds release the moisture back to the earth.
nimbus
Cumulonimbus.
cirrus
CIRRUS
The name altonimbus cloud is Latin for "mid-altitude raincloud." "Alto-" is a prefix that means "mid-altitude" and "nimbus" means "clouds that produces rain."