Wiktionary
substellar
a. (context astronomy of an object English) Having a mass less than the minimum necessary mass for hydrogen fusion
Usage examples of "substellar".
In the elaborate and always growing catalog of substellar astronomical objects, neither the moon nor its parent world were especially impressive.
It seemed to him that the object was falling too slowly to be a meteorite, but what did he know about representative intraatmospheric velocities of terminal substellar objects?