A Homonym

1. (semantics, strict sense) A word that both sounds and is spelled the same as another word. Homonym - Wikipedia
2. (loosely) A word that sounds or is spelled the same as another word (but not necessarily both), technically called a homophone (same sound, different spelling) or a homograph (same spelling, different sound), or if both are the same, a homonym.
3. (taxonomy) A name for a taxon that is identical in spelling to another name that belongs to a different taxon.

Usage notes

• Homonyms (in the broader sense) are divided into the two overlapping subcategories homographs and homophones. Examples:
  • die and dye (homophones but not homographs)
  • the parasitic flatworm called the fluke, the fish called the fluke, and a fluke, part of the tail of a whale (both homophones and homographs and therefore true homonyms in the strict sense)
  • the metal lead and the present tense of the verb lead (homographs but not homophones)