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3.
A poo
"Man, I just did a massive bum baby"
by hgutj January 07, 2012
 
1.
Noun: A derogatory term used to describe someone who is so retarded that they were likely conceived as an atrociously tragic accident through penetrative bumsex.
Bill: Did you see Ali on Friday night acting like a complete donkey?
Ted: Yes! She's such a fucking bumbaby.
Bill: Dude. Sweet call.
by psuedonymtastic adventures July 26, 2011
 
2.
when one visits the bathroom to relieve ones self of bodily waste, they are giving birth to bum babies. Bum babies come in all kinds of varieties, brown, greeney-brown, fat, thin, nutty, the list goes on...
Vicki, I just gave birth to a bum babies, it was so beautiful that a tear of joy rolled down my face.
by Dave matthams January 24, 2007