A social networking site in which you 'follow' people to see what they're doing. In simple terms, a site on which you stalk people to know what they're doing every moment of their lives.
Girl: Robert Pattinson is in Italy at the moment.
Girl 2: How do you know?
Girl: Twitter.
Girl 2: Oh.
A trick of the Devil in the form of an online platform provided to a fool for shouting about inanities other fools are already familiar with, being them their own as well.
The idea that twitting is actually communicating is becoming more and more the foundation of the modern, industrialized society, and it is eminently worthy of the superstructure.
Twitter samples:
@jerryo: fantastic article on social media @ respectyourbrainandgiveupyourcurrentlifestyle.com/quittwitting/howtostart