indiscussible

or in·dis·cuss·a·ble

[ in-di-skuhs-uh-buh l ]
/ ˌɪn dɪˈskʌs ə bəl /

adjective

unsuitable for or not subject or open to discussion; not negotiable.

Origin of indiscussible

First recorded in 1890–95; in-3 + discussible