In sports (real and fantasy) a term used to describe a trade where the other side got nothing of any real value in return.
"Philadelphia traded their whole team to New York for nothing but a box of rocks."
"Derek is trying to get Joe's best outfielder, second baseman and pitcher for a box of rocks."
In sports (both real and fantasy) a player with a high salary that underachieves or performs below expectations. This player ties up a considerable amount of salary under the salary cap, hence the name cap hog.
"Smith is only scoring 3 points a game. We need to get rid of him, he is just a cap hog at this point."
"I need to get Johnson off of my team, he is just a cap hog at this point."