Below are the words that matched your query...
Unhearable
- impossible to hear; imperceptible by the ear; "an inaudible conversation"
Unsounded
- not made to sound; "the silent `h' at the beginning of `honor'"; "in French certain letters are often unsounded"
- 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"
Ultrasonic
- having frequencies above those of audible sound
Unheard
- not necessarily inaudible but not heard
Unfortunate
- not auspicious; boding ill
- unsuitable or regrettable; "an unfortunate choice of words"; "an unfortunate speech"
- not favored by fortune; marked or accompanied by or resulting in ill fortune; "an unfortunate turn of events"; "an unfortunate decision"; "unfortunate investments"; "an unfortunate night for all concerned"
- a person who suffers misfortune
Unpromising
- unlikely to bring about favorable results or enjoyment; "faced an unpromising task"; "music for unpromising combinations of instruments"
Unauthorized
- not endowed with authority
- without official authorization; "an unauthorized strike"; "wildcat work stoppage"
Unauthorised
- not endowed with authority
- without official authorization; "an unauthorized strike"; "wildcat work stoppage"
Unaccredited
- lacking official approval