One who fails to realize the reality of a situation, and instead continues to support/ballyhoo a person, program, etc.
The sunshine pumper sees that their team and coaches are playing hard equating to good, when in fact the players are not performing adequately and the coaches have failed to properly recruit/train/coach the team.
A cousin pumper is a person who fucks their cousin. Typically these people originate from southern United States.
Bill: "dude did Brandon tell you about that chick Tia he banged last week?"
John: "Tia is his cousin, man..."
Bill: "gross that guy is a cousin pumper?!"
A man who constantly wants to bang a bbw, those who love women with more to love, one who fantasizes about sexual encounters with big women, or those of us who are lucky enough to be able to fill one up on a regular basis.
I can't stand when my bbw girlfriend goes out of town, all I can think about is banging her, I am a true plumper pumper,