1. What does it mean?
찐 is a punchy informal way to say something is real or genuine. It can stand alone as 찐이다 or attach to another word, such as 찐친 for a genuinely close friend.
Also written or said as jjin
2. The nuance
It often expresses the speaker's confidence or enthusiasm, not verified authenticity. In a recipe, 찐 can instead be the ordinary form meaning 'steamed,' as in 찐 감자; context separates the two.
3. Examples
“말만 하는 줄 알았는데 매일 연습하네. 너 찐이구나.”
I thought you were just talking, but you practice every day. You're the real deal.
“이 가게는 메뉴 하나에도 정성이 보여서 찐이다 싶었어.”
Even one dish showed so much care that I thought this place was the real thing.
Sources
Kookje Daily: Korean expressions
References support the meaning and usage. Example sentences are written for NoCapWiki.