Asteroid

An asteroid is a celestial body smaller than a planetoid, usually having a diameter of 100 kilometers or less. An asteroid belt is comprised of many asteroids.

Following the Earth-Romulan War, Earth constructed several outposts on asteroids to monitor the Romulan Neutral Zone. 

In the 22nd century, Cold Station 12 was located on an asteroid. . This facility still remained on an asteroid in the 24th century.

While describing the Companion's homeworld, Spock once demonstrated the difference between an asteroid and planetoid by saying the homeworld was "more than an asteroid", "like a small planetoid." 

In 2268, the USS Enterprise encountered the Fabrini ship Yonada, created inside a hollowed-out asteroid. 

The second phase of the Genesis Project was conducted in a hollowed-out section of the Regula asteroid. Starfleet Corps of Engineers completed the hollowing-out and constructing the facility. (Star Trek II: The Wrath of Khan)

James T. Kirk and Leonard McCoy, found guilty by a Klingon court of law for the assassination of Gorkon, were sentenced to the Rura Penthe penal asteroid in 2293. They later escaped when the USS Enterprise-A rescued them. (Star Trek VI: The Undiscovered Country)

In 2370, after a Romulan warbird sealed them inside, the USS Enterprise-D passed through an asteroid using a phasing cloak. 

The Badlands housed many asteroids, including some with a Class M atmosphere. 

The Dominion often used asteroids to construct facilities on or around. Examples include internment camps like Internment Camp 371 and ketracel-white facilities. 

Croden claimed the Chamra Vortex held millions of asteroids, a larger one of which concealed his daughter Yareth.