Someone who only cares for appearance and lacks personality, they are into all the latest trends and shun people who are not the norm(unless they can use them for something). Jamtarts are often under 120 pounds and are usually seen in malls or popular bars wearing shirts too small for them, alot of pink, and have shoes less than 2 months old. They enjoy drinks with straws and standing around where they'll get the most attention.
They are also known to have poor spelling and grammar, and often talk without end about their dating habits or things they have recently purchased.
Jamtarts often don't know you're insulting them even when you do it to their face.
"Come on Ned, let's go to the bar and pick up some Jamtarts!"
"While walking through the mall, crowded with people, we happened upon a fashionable clothing store, completely infested with Jamtarts."