The Oxford American Dictionary has named "unfriend", a verb meaning "to remove someone as a friend on social networking sites such as Facebook" as its 2009 word of the year.
The new word has real "lex-appeal" according to Oxford's US dictionary spokeswoman, senior lexicographer Christine Lindberg.
"It has both currency and potential longevity," she said.
"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."
Ms Lindberg said that most 'un-' prefixed words are adjectives such as 'unacceptable' or 'unpleasant' while there are other familiar 'un-' verbs such as 'uncap' or '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!)."
Twitter also provided some new favourites including hashtag - a hash sign added to a word or phrase that enables Twitter users to search for tweets
Other word of the year finalists included:
* intexticated - distracted because texting on a cellphone while driving a vehicle
* sexting - the sending of sexually explicit texts and pictures by cellphone
* funemployed - taking advantage of one's newly unemployed status to have fun or pursue other interests
* zombie bank - a financial institution whose liabilities are greater than its assets, but which continues to operate because of government support
* deleb - a dead celebrity
* tramp stamp - a tattoo on the lower back, usually on a woman