The Collaborative International Dictionary of English v.0.48:
Unvanquishable \Unvanquishable\ See vanquishable.WordNet (r) 3.0 (2006):
unvanquishable adj 1: incapable of being overcome or subdued; "an invincible army"; "her invincible spirit" [syn: invincible, unbeatable, unvanquishable]