Glossary entry

n.
The highest ranked category employed in the taxonomic hierarchy. (Previous editions of the Code referred to a single taxon "Animalia", not widely accepted today, at the rank of kingdom).

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