Definitions

1. noun

The state or quality of being cloudy or misty, especially in reference to the atmosphere or a celestial body; a cloud or cloudy appearance.

“The nebulosity of the gas giant made it difficult to observe its surface.”

2. noun

A cloud or cloudy appearance of a celestial object, such as a star or nebula, as seen in astronomy.

“The astronomers studied the nebulosity of the newly formed star.”