The phrase "chink in armor" is used to describe a weakness or vulnerability in one's defense or protection. Antonyms for this phrase would be "strength," "fortress," "impenetrable," or "invincible." These words convey an image of a sturdy, unyielding defense that cannot be breached. When it comes to matters of security or protection, having an impenetrable fortress can be crucial. However, it is also important to remember that no defense is foolproof, and everyone has weaknesses. It is important to identify and address any chinks in one's armor in order to maintain a strong and resilient defense.