undiscoverable

About 0.04 uses per million words.

Meaning

1. adjective Unable to be discovered; hidden perfectly.
2. adjective Not subject to being produced in response to a discovery request.

Similar words

unascertainable undeterminable indeterminable indiscoverable uncoverable undetected undiscovered unrevealable undetectable unseen

Often followed by

by in and to as essence reason at chamber