Except even that is inaccurate. Node.js is essentially an abstraction around Chrome's JavaScript engine (V8). Everything else is just a bunch of bells and whistles.
Every programming language is just an abstraction around machine code. Everything else is just a bunch of bells and whistles Node.js is a language, simply for the fact that it has a different domain of developer knowledge and it has it's own runtime (which is built onto V8). Yes, it is built onto another language. Yes, it is just Javascript with bindings to native code. But that doesn't mean it's not a language. Look at how many languages are built onto the JVM. Look at how many language are built onto the LLVM. Each language introduces some new convenience for developers. I suppose a line must be drawn between a library and a language. If Node.js was approached differently, it could have easily become a library. It is, in effect, a set of extensions for V8. But as it is, Node.js is a superset of Javascript, which makes it it's own language.