What does Nimbus signify in cloud terminology?

In cloud terminology, Nimbus refers specifically to rain clouds. The term originates from the Latin word for "rain." Clouds that are described as "nimbus" are generally associated with precipitation. For instance, clouds such as nimbostratus and cumulonimbus are known for their capacity to produce significant rainfall.

While there are various types of clouds with different designations that signify features such as altitude or air circulation, the defining characteristic of nimbus is its association with moisture and precipitation. This makes the choice of rain clouds the most accurate answer regarding the significance of "Nimbus" in the context of cloud types.