In order for olive oil to have an extra virgin grade, it must be fruity, bitter and peppery, have a pleasant taste, and leave a clean feeling in the mouth. It can't be rancid, vinegary, greasy, or smelly. Unfortunately, most of what is on the supermarket shelves currently is not extra virgin (even though it's marked that way right on the bottle) but adulterated oil. Any flaws and it's classed as lampaste which means that it can only legally be sold as fuel. Fake olive oils are worldwide (many are not even made with olives) and the United States sells tons of it.
Most of this fraud is not regulated so it's rampant.
Tom Mueller has written quite an astonishing book. Search the DCLS catalog