1. (as stated by Wikipedia, the best source to fuck with your teachers): a two-pair poker hand consisting of the black aces and black eights. The pair of aces and eights, along with an unknown hole card, were reportedly held by Old West folk hero, lawman, and gunfighter Wild Bill Hickok when he was shot and killed.
2. When an individual has some catastrophic blackmail on someone else but only chooses to use it as a last resort (loosely based off Russia's dead hand (go look that up))
Person 1: Yo, how did Mark get fired? Wasn't he a model employee?
Person 2: Yeah, but he was fucking with the wrong guy for too long, then that guy recorded him saying some of the foulest fucking shit ever, and then he showed their boss.