ig-NEH-sis
Here's a breakdown:
* ig-: Pronounced like the "ig" in "pig"
* NEH-: Pronounced like the "neh" in "nest"
* sis: Pronounced like the "sis" in "miss"
Of course, there might be other variations depending on context or specific usage. If you encountered the word in a specific work, it's always best to check the pronunciation guide or audio if available.