If you describe something as unseen, you mean that it has not been seen for a long time. a spectacular ballroom, unseen by the public for over 30 years We print a selection of previously unseen photos from the Spanish rider's early years
You can use unseen to describe things which people cannot see. For me, a performance is in front of a microphone, over the radio, to an unseen audience There was barely time for the two boys to escape unseen. not noticed or seen. a piece of writing that you must translate into your own language in an examination