1. What does it mean?
겜잘알 means a person who knows games well. It praises knowledge of mechanics, strategy, design, or player preferences, rather than only fast reactions. It is the positive counterpart to 겜알못.
Also written or said as gemjaral
2. The nuance
It can be sincere praise or ironic when someone's advice fails. Expertise in one game does not automatically imply expertise in every genre.
3. Examples
“설명 듣고 보니 너 진짜 겜잘알이네.”
After hearing your explanation, I can tell you really know games.
“겜잘알 친구가 내가 좋아할 만한 게임을 골라 줬어.”
My game-savvy friend picked a game I would enjoy.
Sources
References support the meaning and usage. Example sentences are written for NoCapWiki.