1 definition by Natasha Radical

Top Definition
This is the name given to a very fat person's stomach when it hangs down low and has a crevice in the middle that resembles a bum crack.

The word is an amalgamation of "tummy" and "bum".
You don't have a dad because he got lost in your mum's bummy.
by Natasha Radical July 13, 2010

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