Asteroid
An asteroid was a chunk of rock in space, large compared to many things but small compared to planets and stars. They were similar to, but not to be confused with, comets and planetoids, and were usually located in asteroid belts.
While many asteroids were barren and lifeless, some had life such as the Fire Trap. Its native Sycorax also fashioned starships out of other, smaller asteroids. (DW: The Christmas Invasion)
Other asteroids were centres of trade, such as one on which the rare metal Baloovium was sold. (DW: Army of Ghosts)
The Ice Warriors dropped an asteroid on Paris in 2086; this was the beginning of the Thousand Day War. (NA: GodEngine, BNA: Beige Planet Mars)
The Daleks were able to disguise their saucers as asteroids to fool their opponents upon their approach. (GN: The Only Good Dalek)
Demon's Run was an asteroid. (DW: A Good Man Goes to War)