"A compiler is a computer program (or set of programs) that transforms source code written in a programming language (the source language) into another computer language (the target language, often having a binary form known as object code)"
It's even sourced. There's nothing here saying that "target language" can't be another high level language; and if you look at CoffeeScript (for example) implementation you'll see that it's structured as any other compiler would be. I think "transpilation" would be a bit more precise, but I don't think "compilation" is incorrect term.
