IPA: /ˌɪn.dɪˌfɛn.səˈbɪl.ɪ.ti/
KK: /ɪnˌdɛfənˈsɪbɪlɪti/
The quality of being unable to be defended or justified.
The indefensibility of his actions led to widespread criticism.
Indefensibility is formed from "in-" (meaning not), "defensibilis" (from Latin, meaning defensible or able to be defended), and the suffix "-ity" (meaning the state or quality of). The word refers to the state of being not able to be defended or justified.
Think of 'not' ('in-') being combined with 'able to be defended' ('defensibilis') — this helps you remember that indefensibility means the quality of being unable to defend something.