Basically smartage is a state of mind, that you reach by being dumb, incompetent or just simply stupid.
It is basically the opposite of being smart (eventhough the name might imply otherwise).
A good play of words would also be shortage that you could associate with a brain short circuit, which in other words would then lead to smartage.
- *Friend says dumb stuff* -> "You have just reached smartage"
- *Something stupid happends* -> "Smartage"
A nicer way to say smart ass. You can use this in an office or when kids are around instead of saying smart ass or if you are a stick in the mud and don't cuss.