As far as unique definitions go, Twitter wins hands down in terms of the new definitions that seem to be generated daily! One term which you may not have heard of (but may well have experienced if you are involved in any Social Media Management) is link hijacking. This can take many forms, but is basically when users take advantage of the URL shortener. For example, if I found something interesting on a website that I wanted to share with the Twitter community, I might write something link this:
Interesting article on BBC news about SPAM | “shortened URL here”
Instead of then providing a link to the mentioned article, a really bad link hijacker will link to a completely different page as way of increasing traffic (normally a dodgy page that is difficult to promote). This is a sure fire way to lose followers and also to get banned from Twitter. However, a more common form of link hijacking is when the link takes the user to a landing page, and then a second link is required from the landing page to the article. This again is used for increasing site traffic (there is normally Adsense or similar display advertisements on the page) in order to increase revenue, although many site owners claim that they are doing it as a way of tracking how many users click on their Tweets. This is unnecessary however if you use a service such as TweetBurner which will automatically track this for you.
Digg.com used to automatically add landing pages to their URL shortener, until it received a lot of bad press about “Digg hijacking our Twitter links”. Digg.com have now altered how the shortlinks work slightly, however this is still a sore issue for a number of loyal Digg.com users.