When you poke someone in their hinder hole when they least expect it. Works best when an individual is under a table. The ensuing reactive jump from the "pooperpoke" should cause the victim to jump and drive their head into the bottom of the table.
I caught Joe under the desk picking up a pencil and I pooperpoked him. He now has a concussion.
When you have raunchy anal sex with monkeys and then have the 4 egg special in a rundown Dennys in South Central LA. You then go on to buy 19 cherry (NOT Apple) pies and rape them with a thorny dildo. Afterwards you stay up for over 3 weeks watching Avatar the Last Airbender whilst eating sumptuous ammounts of frozen peas.
Translates to: "not super duper." A purposely mediocre-sounding rebuttal to use on someone expressing enthusiasm for a mediocre event. Can be used sarcastically or merely ambivalently.
"Hey, let's go out to Greasy's and get hot dogs. How's that sound?"
"Mmm. Poop-er dooper!" (w/ sarcasm)
"Pooperdooper." (w/ ambivalence)