A term commonly used by computer and game techies as a type of insult very loosely used. It consists of a statement turned into a suggestive insult by simply adding You *insert phrase here* your mom. This insult can be thrown back and forth with different objects of the insult with the same phrase.
Dude number one: I was looking at the clock earlier...
Dude number two: You clocked your mom!
Dude number one: you clocked your mom's mom
dude number two: you clocked you dad!
dude number one: you clocked you dog's papa's baby's momma.
dude number two: dude, you just dissed my girlfriend.