Is Pluto a planet?
Basic definition: Planets go around a sun. Moons go around planets. Don't ask me what you call something that goes around a moon. Pluto is a planet. It may have been a moon a long time ago. Who knows?
If Phobos (about 20 km dia.) and Deimos (about 15 km dia.) can be called "moons," then pretty much any large chunk of rock going around a planet could be called a moon. Gas giants like Jupiter also have rings that, for all I know, contain chunks at least this size. Jupiter probably has hundreds of things that could be called "moons." When we get out there, I'm sure observers will have names, or at least numbers, for all of them.