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It's when you don't have to take a dump for days, then you visit your parents house, and you MUST take a dump. Even adult children are unaware this is happening but it's definitely umbilically connected. An umbilical dump.
Child: Hey Ma, I feel an umbilical dump coming on.
Ma: Oh shit, I have to clean the skidmarks out of the toilet again?? Another umbilical dump.
by CJMO November 15, 2006