fetter
Meaning: to chain, restrain
Usage: The dog was fettered to the parking meter.
constrain
Meaning: to forcibly restrict
Usage: The rules constrained the team from changing its design after submission.
impregnable
Meaning: resistant to capture or penetration
Usage: Though the invaders used battering rams, catapults, and rain dances, the fortress proved impregnable and resisted all attacks.
impervious
Meaning: impenetrable, incapable of being affected
Usage: Because of their thick layer of fur, many seals are almost impervious to the cold.
resilient
Meaning: able to recover from misfortune; able to withstand adversity
Usage: The resilient ballplayer quickly recovered from his wrist injury.
tenable
Meaning: able to be defended or maintained
Usage: The department heads tore down the arguments in other people’s theses, but Johari’s work proved to be quite tenable.