Even if that meant something in the past, it really isn't a useful definition any more, because pretty much all languages do this. That's why I offered my alternative description. Even if it too has flaws, I think it's a more meaningful description.
sremani != ZenoArrow (though if you read this sremani, thank you for attempting to clarify).
There are many 'multi-paradigm' languages, and C# is one of them. From the C# Wikipedia page...
https://en.wikipedia.org/wiki/C_Sharp_(programming_language)
"C# (pronounced as see sharp) is a multi-paradigm programming language encompassing strong typing, imperative, declarative, functional, generic, object-oriented (class-based), and component-oriented programming disciplines."
What makes a language 'functional' is first-class functions (i.e. functions that can be treated as values, which is what I was referring to in my earlier post).
As sremani said, F# is 'functional first', in the sense that the language is designed to make functional algorithms straightforward to express. You can write C# in a functional way too, but there's less syntactic sugar for this style of programming.
Hope that clears it up.
Ultimately, we have to live in a world where words are kind of ambiguous, but I think we should try to avoid useless definitions. The definition where "a functional programming language is one that can pass functions around" is extremely useless, because it applies to every modern programming language including C and C++. Whatever you want the term to mean, it shouldn't be that, because that distinguishes nothing.
It's not extremely useless when you consider most programming languages cover multiple PL paradigms.
Functional languages are a spectrum. On one end you have pure functional languages like Haskell where you're forced to use functional algorithms for all computation, but there are languages in the middle of that spectrum like C# which support a bunch of functional language constructs (take a look here for a selection: http://www.codeaddiction.net/articles/13/lambda-expressions-... ) even if they aren't purely functional.
My argument is, any definition of functional programming that ignores the mid part of the spectrum is useless, as it ignores that most languages do not strictly follow a single approach like Haskell but allow you to adapt to different styles (i.e. most programming languages are multi-paradigm). Even F# and Ocaml allow you to write in an imperative style if you so choose, and many people would class them as 'functional' languages.
