IMO the key concept is really ambivalence, blurring traditional social roles, pushing or stretching limits or boundaries that were once rigid. Transgender things like cross-dressing that go from one extreme to the other are a significant part of that, but only a part.
In a quick web search on this I was surprised to see how widespread 'gender' and its compounds now are in German. I had been sort of avoiding it, trying to forestall the usual cries of outrage over anglicisms and imports from English, with which I can certainly sympathize, but in this particular case the English word seems to serve a useful purpose.
Native speakers: How would you rate the above paraphrases/explanations? And if the foreign word were just imported, would it clearly be 'das gender-bending,' or could arguments be made for other, er, genders?
On a related topic, I agree that words like geschlechtsfrei, geschlechtslos, and geschlechtsunabhängig aren't the same as gender-bending, but where do they fit in? Do they mean roughly the same thing as each other, or are there slight differences?
@taciturn: In (post)structuralist literary criticism, 'sign' is often a technical term originating in semiotics. But don't do a web search on this, you probably don't really want to know. <G>