[croes]

IR = Intermediate Representation

https://en.wikipedia.org/wiki/Intermediate_representation

[hootz]

Writers really should remember to write acronyms by their full name at least once at the beginning of an article.

[tamimio]

Thank you, half way through the article and I am thinking infrared.

[giorgioz]

I also didn't know the acronym IR. A good solution is passing the URL to ChatGPT and asking "what does IR mean in this url: "