IPA: /ʌnˈnɛɡəʊʤəbl/
KK: /ʌnˈnɛɡoʊʃəbl/
Something that cannot be changed or discussed in terms of agreement or terms.
The price of the car is unnegotiable, so you must pay the listed amount.
Unnegotiable → It is formed from "un-" (meaning not) and "negotiare" (from Latin, meaning to negotiate) and the suffix "-able" (meaning capable of). The word "unnegotiable" means not capable of being negotiated or altered.
Think of 'not' ('un-') being able to 'negotiate' ('negotiare') — that's why unnegotiable means something that cannot be changed or discussed.