Impossible to trace, discover, understand, or examine; unsearchable, unfathomable; inscrutable; = uninvestigable, adj.

Not discoverable; not to be found out; undiscoverable.

(un-, prefix1 affix 1b.)

That cannot be explored; inscrutable.

Not discernible to the mental eye. Obsolete.

Leaving no trace or track; that cannot be traced; of a surface, that shows no traces or lines.

(un-, prefix1 affix 1b.)

Unfindable, undiscoverable; spec. of books. Also as n.

(un-, prefix1 affix 1.)

(un-, prefix1 affix 1b.)