Noun
English Wikipedia has an article on:trinomenWikipedia
trinomen (plural trinomina)
(taxonomy, zoology) A scientific name at the rank of subspecies: an expansion of a binomial name (a genus and a species) combined with the name of the subspecies; for example Anopheles gigas formosus or Homo sapiens sapiens.
Because animals are typically only grouped within subspecies, it is simply written as a trinomen with a third name. Source: Internet
In zoology, the only rank below species is subspecies and the name is written simply as three parts (a trinomen). Source: Internet