Is there a name for words which are pronounced differently depending on which definition is being used?

Solution 1:

As Greg said in his comment, it is important to remember that they are different words even if they happen to share an English spelling. This should help you to come to the definition of what to call them.

These are called homographs that are heterophones. Derived from homo (same) -graph (write) and hetero (different) -phone (sound).

A homograph (from the Greek: ὁμός, homós, "same" and γράφω, gráphō, "write") is a word that shares the same written form as another word but has a different meaning. When spoken, the meanings may be distinguished by different pronunciations, in which case the words are also heteronyms.

Solution 2:

I think Ian Macdonald has identified the essential point: if words can be distinguished reliably (whether by spelling or pronunciation) they are not the same word. But that's a big if; for example, in Britain a fillet is pronounced the same way whether you refer to a fillet steak or a strip of metal. If the last two letters are to be pronounced "A" you need to use one L, and italicise to indicate that you are using a French term (or conceivably a McDonald's trademark, which neatly sidesteps misleading advertising laws).