IPA: /ˌɪndɪˈtɜːrmɪnəbl/
KK: /ˌɪndɪˈtɜːrmɪnəbl/
Something that cannot be determined, measured, or settled clearly.
The outcome of the experiment was indeterminable due to various unpredictable factors.
Indeterminable is formed from "in-" (meaning not), "determinare" (from Latin, meaning to determine), and "-able" (meaning capable of). The word describes something that is not capable of being determined or defined.
Think of 'not' ('in-') being able to 'determine' something — that's why indeterminable means something that cannot be determined.