Fortunately we have this important story to establish an agreed-upon definition for “backfat”:

The graffiti tag “Backfat” — ranging in size from a few inches to a few feet wide — has been popping up on buildings, storefronts, awnings, even between subway tracks, all over Windsor Terrace and Kensington.

. . .

“Backfat” is a colloquial term for the rolls of extra weight that bulge along the edges of a too-tight or ill-fitting bra.

A city official who is familiar with the situation said the law is hot on the tagger’s heels.

“The police are on Backfat’s trail. It is being thoroughly investigated and we are coming close to finding him,” the source said.