A term does not necessarily become meaningless when it applies to a lot of things. "Functional" might be a broad category after all, not the exclusive name of a subset of functional languages. And if your language allows different paradigms, it will be called "functional and imperative and object-oriented... ". At best, if a property is so common that most language have it, it can be assumed to be satisfied by default. As for "procedural", the definition on wikipedia is a little more precise and does not apply to all languages: https://en.wikipedia.org/wiki/Procedural_programming.

That doesn't make the term meaningless, it just means that "functional programming" is a victim of its own success.

If you can apply the term to every programming language in widespread use today[1], then yes, it is pretty useless. There is real value in having the term "functional programming" be meaningful and denote a certain class of languages; defining that as "any language with first-class function values" is too broad as to render the term meaningless.

[1] Even C has this with Apple's Blocks extension (http://clang.llvm.org/docs/Block-ABI-Apple.html).