JAG is a 'DiSism'.
'Stop JAG-ing about Craine'
-Short form of jag-off.
-Similar to a dickhead.
-Not to be confused with wanker, which has an implication of ineptitude.
-Used mainly by Americans from cities between Chicago and Boston.
"Your father is sleeping on the couch because he is acting like a jag."
"The President is a jag."
Within the competitive Surf Life Saving movement of Australia; to jag someone is to catch up to someone who is leading the racing pack by catching a wave from the back of the racing pack. Though legal competitively, it is often frowned upon due to it's lack of effort after the leader put in considerably more effort in actually getting to the front by themself.