backbacon is the fat that hangs over a woman's bra straps in the back. this is usually apparent for several reasons:
1)her bra and/or shirt is too tight/small
2)she is overweight
3) a combination of all of the above.
fat girls are notorious for back bacon either because they have outgrown their bras or are in denial that they have such bacon...a larger shirt should cover up the incidental back bacon that can occur even on a thinner woman when a bra is pinching.
back bacon has an unmistakable look...while walking behind a woman, you can see the outline of her bra and the resulting fat spilling over the top of the bra in the back, resembling rolly/rippling lumps that resemble bacon or a pack of franks. x2 if the bacon bounces when she walks, sorta like a muffin top
but with the bra vs. the pants