Personally I don't see erotic romance as being anything more than books that tick the necessary genre boxes for both romance and erotica [i.e. true love, hot sex, happy ending]. But, whatever. Different people have different definitions and it doesn't generally cause any problems.
I did run across a definition I really have an issue with [via Lucy V Morgan]: "Romance and erotica are different genres (sexual content aside, romance promises a relationship arc and a happy ending; erotica doesn't. They've blended a bit for erotic romance, which is romance with some rather loose morals)."
Because, yeah, having sex always means losing morals. More sex, less morals: perfect negative correlation. Riiiiight. (Yes, I get this might be meant in a glib, sex-positive, loose-morals-is-good way. But still.)