The description of the word you requested from the astronomical dictionary is given below.
A moon of 10 km diameter at about 8,504,000 km from the planet Uranus. The gravity at its surface is about 0.0002 times as strong as on Earth. The moon goes once around its planet in about 749.3 days. The moon was discovered in 2001. Also called UXXI (Uranus twenty-one). Its provisional designation was S/2001 U1.