The description of the word you requested from the astronomical dictionary is given below.
A moon of 2 km diameter at about 21,069,000 km from the planet Jupiter. The gravity at its surface is about 0.0001 times as strong as on Earth. The moon goes once around its planet in about 624.6 days. The moon was discovered in 2003. Also called JXL (Jupiter forty). Its provisional designation was S/2003 J21.