Enter a clue or pattern or both:
The Clue
Like some vaults (9 letter answer)
The Answer
FIREPROOF
Tags
Notes
The answer FIREPROOF is so rare that it appears less than once every 2500 puzzles.
Definition
FIREPROOF as a verb:
1. make resistant to fire
FIREPROOF as an adjective:
1. impervious to damage by fire