A meteoroid was a piece of astronomical debris, smaller than an asteroid.
In 2254 José Tyler proposed meteoroids as the source of the unusual readings. (TOS: "The Cage")
The probe Nomad suffered a serious loss of memory after a collision with a meteoroid. (TOS: "The Changeling")
In 2262, the SS Beagle suffered serious damage from a storm of meteoroids. (TOS: "Bread and Circuses")