Oxford Dictionary

Thanks to Facebook, “unfriend” will soon be appearing in what has long been considered the ultimate reference work in American English lexicography. The New Oxford American Dictionary has chosen to legitimize the once grammatically-questionable word by naming it the 2009 Word of the Year. A verb, “unfriend” is defined as “to remove someone as a ‘friend’ on a social networking site such as Facebook.” 300 million Facebook users can’t be wrong!