Two or more words spelled differently but pronounced the same are called homonyms by logologists. Today's linguistics appears to have no name for such words - homonyms, homophones, and homographs may or even must all be spelled and sounded alike.
Borgmann, Dmitri A.
"The Ultimate Homonym Group,"
Word Ways: Vol. 17
, Article 9.
Available at: http://digitalcommons.butler.edu/wordways/vol17/iss4/9