It can be many things. If by "unseen" you are portraying something.. 1. unnoticed - as in :you sneaked into a house unseen" 들키지 않고, 아무도 못보게 or as in "unseen danger ahead": (미처) 보지못한, 내다보지 못한 or as in "sight unseen" 보지 않고, 안보고 2. that is extraordinary to the extent that it has never been seen, like unseen talent 전무후무한. 한번도 보지 못한 pick ur pick

I don't know which means Unseen. If it is formless&invisible, it is 무형. 무형은 형태&보이지도 않고 추상적인 개념을 무형이라 할 수 있어요, 그리고 한자에요~