Infrangible [adjective]
Definition of Infrangible:
strong, tough
Sentence/Example of Infrangible:
Here Vulcan forged those infrangible chains, that impenetrable armor—the shield of Achilles and the sword of Hector.
Frangible things are of less value than things that are infrangible.
He liked this harsh country, these harsh, infrangible people that it bred.
To the heathen Indian, an oath such as this is absolutely infrangible.