When to use boring not fun in Korean
Korean: 노잼[ no-jaem ]

When to use it
노잼 means “boring” or “not fun.” People use it in casual speech when a movie, game, class, joke, or situation is not interesting. It is slang, so it sounds natural with friends, but not in formal situations.
Example sentences
집에서 혼자 있으니 노잼이야.
Being home alone is boring.
오늘 수업은 좀 노잼이었어.
Today’s class was a little boring.
비 오는 공원은 노잼이야.
A rainy park is boring.
그 이야기 또야? 노잼이야.
That story again? It’s boring.
이 가게는 볼 게 없어서 노잼이야.
This store is boring because there is nothing to see.
기차 여행이 너무 길어서 노잼이야.
The train trip is boring because it is too long.