metaphone
/ˈmɛtəfəʊn/Phonetics
noun
Either of two or more phonemes which are in free variation in particular words or in particular circumstances. Also: (in H. E. Palmer's terminology) a phoneme comprising more than one sound (disused ).
Origin
1930s; earliest use found in Harold Edward Palmer (1877–1949), linguist and teacher of languages. From meta- + phone.