IPA: /ˌʌnɪnˈfɔːrsəbl/
KK: /ʌnɪnˈfɔrsəbl/
Not able to be enforced or made to happen, often referring to laws or agreements that cannot be applied or upheld.
The contract was deemed unenforceable due to its vague terms.
Unenforceable → It is formed from "un-" (meaning not), "enforce" (from Old French *enforcier*, meaning to strengthen or make effective), and "-able" (meaning capable of). The word describes something that is not capable of being enforced or made effective.
Think of 'not' ('un-') being able to 'make effective' ('enforce') something — that's why unenforceable means it cannot be enforced.