If established name doesn't exist, what name you can suggest?
You already seem to have an idea of what the standard names are. The four you've given are widely enough used that I'd go along with them unless you have some fairly specific reason to do otherwise. Of course, some depends on what "family" of languages you're talking about. Some terms are more widely used than others. Just for example, "special form" will probably be meaningful if your audience is users of Lisp and similar languages, but otherwise it might do more to obfuscate than clarify.