Unguessable

Origin

- + guessable

Full definition of unguessable

Adjective

1. Not capable of being guessed.
• 2001, Simson Garfinkel, Gene Spafford, Web Security, Privacy and CommerceEspecially bad are "magic words" from computer games, such as xyzzy. These magic words look secret and unguessable, but in fact they are widely known.