Unlike the term lobster, which refers to the british soldiers' bright red uniforms, "lobsterback" refers to the scars on the soldiers' backs. Whipping or flogging was common in the british army, and used for pretty much any diciplinary problems. Almost all Bristish troops had scars from numerous lashings.
British Soldier: Go to hell.
2) Slang for an annoying british person who is arrogant and cant stop boasting about how much better there country is than america.