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.
1. Person A: Are you ok? Person B: Mef
2. Person A: Is something wrong? Person B: Mef
3. DVD fails to record a tv program you wanted to see but could catch another time 'mef' said outloud