invulnerable
in-vul-ner-a-ble
adjective
Impossible to harm, damage, or defeat; completely protected from attack or injury.
"The fortress was invulnerable to siege."
Thesaurus
Synonyms: shellproof, impregnable, strong, entrenched, defensible, defendable, bombproof, airtight, untouchable, unassailable, unattackable, tight
Antonyms: vulnerable