From the Oxford University Press blog:

Without further ado, the 2009 Word of the Year is:

unfriend

.

unfriend

– verb – To remove someone as a ‘friend’ on a social networking site such as Facebook.

As in, “I decided to 

unfriend 

my roommate on Facebook after we had a fight.”

Other new words recognized by the Oxford University language boffins include hashtag, intexticated, sexting, funemployed, deleb, and zombie bank.

Many of these words a tech words, of course. Should a technical publisher coin new words in their books, when none of the existing ones will do? At Packt we occasionally have to decide whether a word that an author seems to have invented (but that carries a useful meaning) is something we should print, or edit into more pedestrian language.

http://blog.oup.com/2009/11/unfriend/