What's the noun for homonymic? Here's the word you're looking for.
homonym
(semantics) A word that both sounds and is spelled the same as another word but has a different meaning.
(loosely) A word that sounds or is spelled the same as another word but has a different meaning, technically called a homophone (same sound) or a homograph (same spelling).
(taxonomy) A name for a taxon that is identical in spelling to another name that belongs to a different taxon.