1. What does it mean?
쩐다 is a conversational form of 쩔다. It strongly reacts to the quality, scale, or intensity of something. A performance can be impressively good, while an unpleasant situation can be intensely bad.
Also written or said as 쩔다, 쩔어, jjeonda, jjeolda
2. The nuance
It is slangy and can sound rough in formal company. Read what is being described: 실력 쩐다 praises skill, but 냄새 쩐다 complains about a strong smell. It is not always a compliment.
3. Examples
“연습 영상 봤어? 드럼 실력 진짜 쩐다.”
Did you see the practice video? Their drumming is seriously impressive.
“우산도 없는데 비 오는 양 쩐다.”
I don't even have an umbrella, and it's pouring like crazy.
Sources
KoreanClass101: Korean language lessons
References support the meaning and usage. Example sentences are written for NoCapWiki.