A place where you get a massage but most commonly refers to a whore house in disguise of a legitimate massage business. Usually if you see a run down building in the shady part of town with a neon sign saying "MASSAGE", chances are its a rub and tug joint.
"I'm going to a massage parlor Dan, you want to come?"
"No thanks, I'm afraid of getting the clap"
Any business displaying itself as a place to receive a massage, but will offer sexual services...if the price is right. Police may occasionally raid these joints in places where prostitution is illegal (mainly U.S.).
Why date and play all those stupid games with a "girlfriend" when you can go to a massage parlor?