the literal translation is: ur mum's punany!!!! but it means u want to have a wild ride with the mum in question.
its then one of the shortest way to start a nice discussion with an arab guy , discussion that will probably ended with a direct fist in the midle of ur face as the transcription of all the love involved between u and the persone ur talkin to . of course as all insults u can combine it in may ways
kos ommak ya ebn el sharmouta .
koss om abouk el a7beh el men7ata ....
and so on .