uncrackable

adj — 2 senses

adj

Etymology From un- + crackable.

Of a code That cannot be cracked; unbreakable.

Of a safe That cannot be broken into.

I may as well inform you that no crib is really uncrackable, though the Cyrus J. Coy Co.'s Safe Deposit on West 24th Street, N.Y., comes nearest the kernel.1914, Ernest Bramah, Max Carrados:

Entry derived from the Wiktionary, under licence CC BY-SA 4.0 — list of authors.