The Collaborative International Dictionary
never-say-die \never-say-die\ adj. Incapable of being subdued.
Syn: indomitable, unsubduable.
Wiktionary
a. That doesn't give up in despair; indomitable
WordNet
adj. impossible to subdue [syn: indomitable, unsubduable]
Usage examples of "never-say-die".
You would think that Roux and Chamberland, still youngsters, would have been the indomitable ones, the never-say-die men of this desperate crew.
Butterwort and red-and-blue never-say-die clambered up the gullies toward the hillcrests, and white mooneyes covered the ground almost everywhere that grass did not.
Can you see a never-say-die character like Mac-Donald, not only a highly decorated officer who fought in a tank regiment for six years but also a nerveless espionage agent for many years after that, committing suicide when things started closing in on him?