Means: An awkward, unpopular girl
Usage: "Don't hang out with Leah, she's such a meg""Those granny google-eye glasses she wears are just megging."
Teen slang is, of course, all about bigging oneself up while being cruel to outsiders, and Yoofspeak is full of put-downs, slurs and nasty nicknames for those considered less suave and sophisticated. This one is used specifically to diss the earnest, clumsy, socially awkward girl who doesn't quite fit in with your group's aspirations to cool. Junior etymologists will tell you that it derives from the initials M.E.G, for "most embarrassing girl". But it's much more likely to have been inspired by the daughter of the same name in the cartoon Family Guy, or simply by an annoying kid sister somewhere in the real world called Megan or Margaret. Typical of Yoofspeak, the original noun has spun off a new adjective, megging, and a verb, to meg out: "Have you seen Holly's new geek look: she's, like, suddenly megged out." (Most of the boys, by the way, think Holly's strangely cute - but would never say so out loud.)