n (semantics|with respect to a given word or phrase) A word or phrase with a meaning that is the same as, or very similar to, another word or phrase.
n (zoology|with respect to a name for a given taxon) Any of the formal names for the taxon, including the valid name (i.e. the senior synonym).
n (botany|with respect to a name for a given taxon) Any name for the taxon, usually a validly published, formally accepted one, but often also an unpublished name.
n (databases) An alternative (often shorter) name defined for an object in a database.