Yep, software specs or requirements[0]. Thanks to LLMs it's easy to look up acronyms, but still, it feels like there's an uptick of them on HN[1]...

[0] https://en.wikipedia.org/wiki/Software_requirements_specific...

[1] https://news.ycombinator.com/item?id=47323316 who the hell knows that version of "RSI"?