Definitions for unplumbedʌnˈplʌmd
Random House Webster's College Dictionary
not plumbed; not measured with a plumb line.
not understood or explored in depth.
Origin of unplumbed:
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"
Not measured for depth, as if with a plumb.