They assume that everyone knows exactly what it means,

Most importantly, themselves.

and if you ask for a definition, that seems like trolling.

Yes. If you suggest they're conceptually muddled, instead of attempting to demonstrate their conceptual clarity, which should be trivial to do if they have it, they will get huffy and declare you a troll.

That too, actually. Perhaps the word is usually used to mean a set of this all. You know, the wider the meaning, the greater the chance that at least some part of it can be defended successfully in a debate.

That's the true Dark Art. Endlessly equivocate on the meaning of your terms. It's so dark, you can manipulate yourself into believing that you know what you're talking about. See Rand and "life" for details.