unanswerable

adjective

1 an unanswerable case for investment:

irrefutable, inarguable, unarguable, indisputable, undeniable, incontestable, incontrovertible;

conclusive, absolute, positive;

rare irrefragable.

▷antonyms weak, flawed.

2 it was no use pondering on unanswerable questions:

insoluble, unsolvable, insolvable, unresolvable, unexplainable, inexplicable, unascertainable.

▷antonyms obvious.

unanswerable Oxford Dictionary of English