Glossary entry

n.
A group of species, other than a subgenus, within a genus; or a group of species within a subgenus; or a group of subspecies within a species. An aggregate may be denoted by a species-group name interpolated in parentheses [Art. 6.2].

Source:
International Commission on Zoological Nomenclature (1999) International Code of Zoological Nomenclature. Fourth Edition. - International Trust for Zoological Nomenclature, XXIX + 306 pp.