Wiktionary
n. bacon prepared from centre-cut boneless pork loin.
Wikipedia
Back bacon is a traditional British cut of typically unsmoked bacon sliced to include both the pork loin from the back and a bit of pork belly in the same cut. It is either wet- or dry-cured, and is much leaner than American style smoked side bacon made only from the pork belly. Back bacon is derived from the same cut used for pork chops, the loin.
In Australia, back bacon is known as 'middle bacon', not to be confused with 'short cut bacon', which does not include the pork belly. See Bacon#Australia and New Zealand.
Usage examples of "back bacon".
Within OrganInc Farms itself it was noticeable how often back bacon and ham sandwiches and pork pies turned up on the staff café.
I'd kill for eggs over easy with back bacon and a pile of hash browns in the morning along with a glass of fresh-squeezed orange juice.