A tweatup is like a tweetup, but instead of having coffee or drinks while networking, it involves eating food at a restaurant. Typically, a tweatup happens in a locally owned or neighborhood restaurant on a slow night (like monday or tuesday), thus giving much-needed business to the restaurant owner.
A gathering of nerds attempting social contact, likely for the first time. Usually disintegrates into everyone running to the nearest computer to type to one another.
Tommy: Hey Jethro, quit playing WoW its time to meet some folks at the tweetup!
Jethro: Oh yeah I forgotabout that, I can't wait to meet BigBootay421 at the tweetup, but first I need to slay this orc!
twitter + creature. Any user or account on Twitter that is not identifiable by content as being from a human. As apposed to tweeple, a tweature is the class under which all other unclassifiables belong, including spammers, link listers, people with a small following who use twitter like a chat client exclusively for inside jokes, and any other use or service that is unreal or is impersonal.