As do other such companies, the New Oxford American Dictionary has revealed the new words it is considering for inclusion, and revealed its choice of "Word of the Year" for 2009.

The 2009 Word of the Year has been named as "unfriend" with the definition reading "unfriend – verb – to remove someone as a 'friend' on a social networking site such as Facebook".

"It has both currency and potential longevity", says Christine Lindberg, senior lexicographer for Oxford's US dictionary program.

"In the online social networking context, its meaning is understood, so its adoption as a modern verb form makes this an interesting choice for Word of the Year. Most 'un-' prefixed words are adjectives (unacceptable, unpleasant), and there are certainly some familiar 'un-' verbs (uncap, unpack), but 'unfriend' is different from the norm. It assumes a verb sense of 'friend' that is really not used (at least not since maybe the 17th century!). Unfriend has real lex-appeal".

Other words that were considered are heavily influenced by another social networking site - Twitter - with "hashtag" high on the list, while "Notable Word Clusters for 2009" include the following:

Tweeps, Tweetup, Twitt, Twitterati, Twitterature, Twitterverse/sphere, Retweet, Twibe, Sweeple, Tweepish, Tweetaholic, Twittermob and Twitterhea.

Do you know what they all mean?