Webster's Revised Unabridged Dictionary · 1913

Indefectible

Indefectible , adjective

[Prefix in- not + defectible: compare French indéfectible.]

Not defectible; unfailing; not liable to defect, failure, or decay.
An indefectible treasure in the heavens. — Barrow
A state of indefectible virtue and happiness. — S. Clarke