Somebody who considers themself so tied to someone else that they are only there to do the other's bidding. A slave. By analogy with an actual third arm, with which the owner of the arm could hope to do so much more, but which has no independentlife of its own.
Mary is trying to treat Jimmy like her third arm again. She won't even let him go out for a night with the lads.
1. Select a player (real or fantasy) during a sports draft to spite or anger one or more of your opponents because they had intended to select him/her.
2. Select a player (real or fantasy) during a sport draft to put one or more of your opponents at a strategic disadvantage.
1. Billy hate drafted Chad OchoCinco because he knew Sam had wanted him since he is from Cincinnati. Billy already had plenty of players to fill that position but wanted to make sure Sam didn't get him.
2. Billy hate drafted Peyton Manning because he was the only good quarterback left and he knew Sam had been planning on drafting him.