The description of the word you requested from the astronomical dictionary is given below.
A moon of 20 km diameter at about 129,000 km from the planet Jupiter. The gravity at its surface is about 0.0005 times as strong as on Earth. The moon goes once around its planet in about 7.2 hours. The moon was discovered in 1979. Also called JXV (Jupiter fifteen). Its provisional designation was S/1979 J1.