-(으)ㄴ 듯하다
It is added to a modifier '-(으)ㄴ/는/(으)ㄹ' meaning the speaker's 'supposition' '-(으)ㄴ 듯싶다' is a variant form.
Example:
1. 어디서 한 번 만난 듯한데 혹시 저를 모르시겠어요?
It seems that I've met you once, do you recognize me?
It seems that I've met you once, do you recognize me?
2. 친구가 내 눈치만 보는 걸 보니 나한테 숨기는 게 있는 듯싶어요.
Since my friend walked on eggshells around me, he must have something to hide.
3. 부장님이 금방 폭발할 듯한 표정이니까 조심하세요.
Since our manager looks like he's about to explode, please be careful.
4. 이 텔리비전이 고장이 난 듯해요.
This television seems to be broken.
5. 블라우스가 좀 작은 듯해서 살까 말까 고민하고 있어요.
The blouse seems a bit small, so I'm debating whether to buy it or not.