Planetoid was the common designation for a small planet-like celestial object orbiting a star. These planetoids, or minor planets, can maintain their own individual and unique solar orbit, or they can also be found among asteroids in an asteroid belt.
Several planetary classifications have been applied to these bodies including:
Spock once described Gamma Canaris N as "more than an asteroid. Like a small planetoid, I should say." He further described it as "possibly a remnant of a planet breakup." This planetoid was unique due to the fact that it had an atmosphere "practically identical to Earth," as well as a gravity similar to Earth, which was "most unusual for its size." (TOS: "Metamorphosis")