That cannot be vanquished, overcome, or subdued; unconquerable. transferred and figurative (a) of persons in spiritual or mental warfare…

(un-, prefix1 affix 1b.)

figurative and in figurative contexts.

That cannot be overcome.

figurative (from A. 1 A. 2). Of difficulties, hindrances, etc.: That cannot be ‘got over’ or overcome; unconquerable, invincible; forming an…

That cannot be surmounted, overcome, or passed over.

Incapable of being surmounted or overcome; insurmountable. Of difficulties, etc. (Common in 18th cent.)

colloquial (originally North American slang). Incredibly or extraordinarily good or bad.