unbreakable
Definitions
Impossible to break or damage.
Not capable of being violated, ignored, or changed, such as a promise or rule.
Extremely durable or resilient.
Examples
The bond between the two lifelong friends proved to be truly unbreakable.
He designed a specialized case that is virtually unbreakable, even when dropped from great heights.
Despite the intense pressure of the competition, her spirit remained unbreakable.
Synonyms
indestructible durable sturdy tough resilient imperishable solid