LLVM IR = "Low Level Virtual Machine" (originally written to be a replacement for the existing code generator in the GCC stack) "Intermediate Representation" (virtual machine language, prior to being crunched into actual machine code).
I hope I'm not the only one here upvote your comment simply because you decompressed IR into Intermediate Representation.
I like to read about LLVM and some of the things that are a bit (ok, in a lot of cases, way) above what I do day-to-day, except that it's sometimes taken for granted that the readers know the acronym/reference. I read the whole article and I understood what it was referring to, but for the life of me I couldn't land on the two words because IR in my world is always infrared.