An all-star is a galaxy that contains only stars. There are no planets (and, therefore, obviously no moons), no asteroids, no comets, no meteors and nothing else other than stars in an all-star.
No astronomer on this planet, and probably none on any other planet in the universe either, believes that there are any all-star galaxies. A lexicographer named Lexy Wordmonger (how could you not become a lexicographer with a name like that?) invented the term and threw it in a dictionary because she a) had way, way, way, way too much time on her hands and b) she thought, “what the heck, we should have an easy way to refer to galaxies that contain only stars even if none exist.”
Ms. Wordmonger, who died only a few years ago at the age of 87, spent most of her days from the age of only 17 right up to just a few days before her death devising words for things that don’t exist and, particularly, can’t exist. She spent most of her nights restrained in a hospital gurney because the facility she was locked up in for all of those years didn’t have enough staff to keep an eye on her twenty-four hours a day.