Development options are pretty much limited to a dictionary type site. And it can't be a niche site either since it says ALLdefintions. The pool of developers in this area has got to be quite small. But considering the work that would go into such a site and the major project it would be, they'd pay $400 for it's domain.
The question is, what are the chances that a developer is making a site like this AND they want this to be it's domain? I would say, not good. So it's a domain that is more likely to be traded among domainers than ever developed.
I don't see you getting the $400, unless it's from a crazy domainer.