The word tweet, in relation to social media, has been added to the Oxford English Dictionary (OED), breaking the rule which says a new word must be current for a decade before inclusion.
The addition is marked as a 'quiet announcement' on the dictionary's June 2013 update.
Chief editor and lexicographer John Simposon, 59, said: "The noun and verb tweet (in the social-networking sense) has just been added to the OED."
Other new word entries include flash mob, live blog, mani-pedi, geekery and jolly hickey sticks.
Commenting on the word tweet, Simpson said: "This breaks at least one OED rule, namely that a new word needs to be current for 10 years before consideration for inclusion. But it seems to be catching on."
The word has been used only since 2007, the dictionary says, one year after the launch of Twitter.
To tweet, says the entry, is to "make a posting on the social networking service Twitter. Also: to use Twitter regularly or habitually."
The Oxford English Dictionary was first used in 1895.