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1.
The act of defecating while receiving oral sex and smoking a blunt (similar to a blumpkin)
After Evan and Ed shotgunned some beers, they asked Kristen to give them both a blundy.
by BrasANDKras October 12, 2007
 
2.
Bloody underpants, from various reasons.
"Hey man check this out!"
"Ew that's gross, get your blundies away from me"

"I sharted myself last night and when I looked there was blood in there, what should I do?!"
"Hahahaha you got blundies!... Go to the doctor."

"You better go check your blundies because your farts don't smell right son."
by tml 4 life December 19, 2013
 
3.
Slang term for blunder.
"I made a blundy!"

"Yeah I really blundied there, didn't I?"
by saucemonkeys July 29, 2011
 
4.
undies/panties that are different colors- - red undies would be rundies, black/blue undies would be blundies, etc
girl#1- yeah..today im gonna be getting it on so i got on my blundies
girl#2- ur sexy blundies?
girl#1- hells yeaa
by d3bbie June 12, 2004