Synonyms of unplumbed

Adjective

1. profound, unfathomed, unplumbed, unsounded, deep (vs. shallow)

usage: 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"

Definition and meaning of unplumbed (Dictionary)