planetoid
A planetoid (also known as a "dwarf planet" or a "minor planet") is a rocky celestial body that is larger than an asteroid, smaller than a regular sized planet, and is not a natural satellite of a bigger planet (colloquially referred to as a moon).
In fiction planetoids can also refer to small spheres (smaller than a person) that somehow retain the qualities of a planet despite its size such as its own gravity, an atmosphere, and sometimes even microscopic life or civilizations living inside it.
Examples
- Ceres
- Eris
- Pluto