1) A slump buster
2) A name for a sub-par member of your opposite sex in which you "engage in activities" with in order to regain emotional stability after a breakup or sexual prowess after a lengthly period of zero sexual activity with another person.
A) "I totally can't take it anymore, I might just go for the sluster tonight..."
B) "Dude, get her off your mind, tonight we're finding you a sluster..."
C) "Hey Dan, how do you know each other? Oh wait, that was your sluster!"