A person with an inability to use twitter or is unable to tweet. This can also be used to describe a person with difficulty using social media in several varieties (Facebook, MySpace and other blogs)
Other forms of this are twittard.
Adjective - tweetarded, twittarded
I can't believe you can't use your iPhone or something to learn to use Facebook. You're such a twittard.
I can't figure out how to post pictures in my blog. I'm so tweetarded.