(biology) a group of organisms within a species that differ in trivial ways from similar groups WordNet 3.0 & Open English WordNet

In biology, a strain is a genetic variant, a subtype or a culture within a biological species. Wikipedia

In botanical nomenclature, a form is one of the "secondary" taxonomic ranks, below that of variety, which in turn is below that of species; it is an infraspecific taxon. If more than three ranks are listed in describing a taxon, the "classification" is being specified, but only three parts make up the "name" of the taxon: a genus name, a specific epithet, and an infraspecific epithet. Wikipedia

Variants of plants, viruses or bacteria; or an inbred animal used for experimental purposes Wikipedia Disambiguation

A formal taxon at a rank lower than species Wikipedia Disambiguation

Genetic variant, a subtype or a culture within a biological species Wikidata

A group of individuals derived by descent from a single individual within a species. OmegaWiki

In botanics, a group of organisms within a species that differ in trivial ways from similar groups. OmegaWiki

An infraspecific rank. Wiktionary