subspecies

A rank in the classification of organisms, below species.

I believe it [the trilobite Calymene blumenbachii] has been divided into several forms, which cannot claim more than the rank of subspecies, as they pass by slight gradations into forms which no author has yet thought it right to separate from the type species.

Ant taxonomists have decided that anything that's worth separating should be separated at the species level, and have no truck with subspecies at all. Butterfly taxonomists, however, like the triple-barrelled name approach and dote on subspecies. As a result, the numbers of ant species and butterfly species are not directly comparable.

A taxon at that rank, often indicated with trinomial nomenclature (such as Felis silvestris silvestris in zoology and Pinus nigra subsp. salzmannii in botany).

But these slight differences will not justify us in considering the West African chiquera as a true species distinct from the Indian true chiquera; it is only a subspecies of the latter true species.

A subdivision of a species in other scientific disciplines.

Granular Augite. […] This subspecies of augite has been hitherto found principally in primitive rocks at Arendal in Norway, in several of the iron-mines, particularly that named Ulve-Grube.