* It's a typo. Perhaps the intended acronym was something like "T.S.K.", which could stand for something specific.
* It's a very niche acronym. It could be an abbreviation used in a specific industry or field.
* It's a made-up acronym. It could be a playful or personal acronym used by individuals or groups.
To understand what "TSK" means, you'll need more context. Please provide:
* The source where you saw it. Was it in a book, article, website, or conversation?
* The surrounding text. What was being said or written around the acronym?
With more information, it might be possible to figure out the meaning of "TSK."