Definitions for unfathomed
Random House Webster's College Dictionary
profound, unfathomed, unplumbed, unsounded(adj)
situated at or extending to great depth; too deep to have been sounded or plumbed
"the profound depths of the sea"; "the dark unfathomed caves of ocean"-Thomas Gray; "unplumbed depths of the sea"; "remote and unsounded caverns"
Of unknown depth.
Not explored or unknown.
Origin: un- + fathomed