A Web site and service that lets users send short text messages up to 140 characters in length from their cellphones to a group of people. Launched in 2006, Twitter (www.twitter.com) was designed to keep friends and colleagues informed about one's daily activities. However, Twitter is also increasingly used for commercial purposes such as companies telling customers "what's new." In addition, politicians and celebrities use Twitter to keep constituents and fans informed.

Twitter messages ("tweets") are not sent indiscriminately; they are only distributed to recipients who have elected to become followers. Messages can also be sent via instant messaging, the Twitter Web site or a third-party Twitter application. A MySpace account can also be updated.

Twitterers Discuss Tweets at Tweetups
A Twitter message is a "tweet," and people who write tweets are called "twitterers" or "tweeple." A gathering of twitterers is a "tweetup," and a novel written and distributed as tweets is a "twiller." A Twitter follower may also get stung by a Twitter phishing scam (see twishing).

From Mobile Blogging to Microblogging
Twitter expanded "mobile blogging," the process of updating a blog from a cellphone, into updating an activities blog (the "microblog") and immediately sending the updates to followers. See Twittersphere and microblog.