The phrase nomen nudum is a Latin term, meaning "naked name". In taxonomy, this is used to indicate a term or phrase which looks like a scientific name, and may well have been intended to become a scientific name, but fails to be one because it was not (or not yet) published with an adequate description (or a reference to such a description), and thus is "bare" or "naked".
Because a nomen nudum fails to qualify as a formal scientific name, a later author may publish a real scientific name that is identical in spelling. If the same author publishes a name first as a nomen nudum and later accompanied by a valid description, the date of publication of the latter, valid, description becomes the taxon's date of establishment.
The glossary of the International Code of Zoological Nomenclature gives this definition:
- "''nomen nudum (pl. nomina nuda), n.
A Latin term referring to a name that, if published before 1931, fails to conform to Article 12; or, if published after 1930, fails to conform to Article 13. […]"
And among the rules of that same zoological Code:
- "12.1. To be available [that is, usable as a scientific name], every new name published before 1931 must … be accompanied by a description or a definition of the taxon that it denotes, or by an indication [that is, a reference to such a description or definition]. …
13.1. To be available, every new name published after 1930 must … be accompanied by a description or definition that states in words characters that are purported to differentiate the taxon, or be accompanied by a bibliographic reference to such a published statement."
The glossary of the ICBN gives this definition:
- "A name of a new taxon published without a description or diagnosis or reference to a description or diagnosis."