A subspecies was a variant within a species of lifeforms, distinct but not enough to constitute its own species.
Loracus Prime was known to count more than five thousand subspecies of termites. (ENT: "Strange New World")
The Aenar were considered a kind of subspecies of the Andorian species. (ENT: "The Aenar")
According to Aaron Waltke, there might be some subspecies of flightless Aurelians. [1]