The description of the word you requested from the astronomical dictionary is given below.
moon, plural moons
A moon is a celestial body that orbits around a bigger celestial body. The Earth not only has a natural moon (the Moon, 3496 km large, number 14 on the list of largest objects in our Solar System), but also a couple of thousands of artificial moons, launched from the surface of the Earth. Most planets of our Solar System have one or more moons. The biggest planets have more than ten. Another word for moon is satellite. The month is named for the Moon.