Baseball players believe that by having sex with an unattractive female, they can end their slump. Therfore a slump buster is the unattractive female that they have sex with, in hopes of busting their slump.

A large, unatractive, girl, most commonly with low self esteem, incorperated in sex with one that is suffering from a slump. (see slump)

Banging some fat ugly bitch because you CAN. You haven't had any in awhile so a slump buster is what you need to get some confidence back to higher class hizat's. Typically a slump buster is a grenade or a M.U.F.F.

a slutty girl that baseball players have sex with in order to break a slump.

A freshman college girl, who starts the year as a cute beer guzzler at the local fraternity party; who then becomes 20 lbs heavier and willing to go home with any guy who needs a piece of ass.

A female friend that you turn to when you need sum sex 'coz yo' aint been getting much.
Hopefully not, but may often be unnatractive.

A Fun Guy 2 Bust A Move With But In the Real World Is A Slump.