IPA: /ˌʌndɪˈtɜːrmɪnəbl/
KK: /ʌnˈdɪtɜrmɪnəbl/
Something that cannot be determined or decided.
The outcome of the experiment was undeterminable due to various unpredictable factors.
Undeterminable → It is formed from "un-" (meaning not), "determinare" (from Latin, meaning to limit or define), and "-able" (meaning capable of). The word "undeterminable" means not capable of being defined or limited.
Think of 'not' ('un-') being able to 'define' ('determinare') something — that's why undeterminable means something that cannot be defined.