1.
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.
ADJ
2.
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.
ADJ: ADJ n, ADJ after v