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1.
the greasy, dirty buildup of dirt and oil under boobs and between the rolls of fat ppl. especailly when they don't shower.
that fucker is covered in titty butter
by jay May 31, 2003
 
2.
The greasy goo that accumulates under the breasts of fat chicks if they don't have good hygiene. Attributed to that musty smell that huge bitches tend to have.
Hey bitch, wash that titty butter off yourself.
by zack February 23, 2003
 
3.
The matured and processed product of a woman's breast milk.

The breast milk can be churned into butter simply by massaging the woman in question's tit and then leaving it to mature over night.
'mmmmm Oz's Mummy's titty butter's a real treat on toast'

or

'is this cake icing made from titty butter?'
by Pat Churner February 26, 2008