unsounded

adjective

1
not made to sound
the silent `h' at the beginning of `honor'
in French certain letters are often unsounded
2
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

Also useful for “unsounded”:Unscrambler— Rearrange the letters in “unsounded”