mef-derived from the insult meffa or indeed mephloid.
Someone of limited inteligence/extreme clumsyness.
or indeed someone whose limited spacial awareness and general geekiness makes them satnd out from the crowd of geeks
A word of no meaning other to certify you heard what the other person said, it conveys no emotion. Most commonly used on an instant messenger to stop someone bothering you. Can be used in place of swear words in everyday life.