My definition of an advanced dive will fit all levels of divers.
An advanced dive is any dive that is towards the upper end (or beyond) of your training, your comfort level, or your abilities.
Each diver may very well have different "advanced levels" from one day to the next even if it is the same dive site.
I had an interesting experience in this regard a couple of weeks ago. I was diving with two friends in pretty benign conditions off the Yucatan coast in Akumal. The boat rides were short, so we would go out, dive, and come back to shore between dives. One day we did a morning dive, and the DM said that he noticed we were the only ones signed up for the afternoon dive, and he wanted to take us to a site that would be more interesting and more suited to our abilities. As we prepared to get on the boat that afternoon, we were concerned by the fact that another couple had signed up for the dive, and they did not seem to have a lot of experience.
Sure enough, they only had about 20 dives each, and buoyancy was an issue. For the first 5 minutes of the dive, the 3 of us hovered nearby as the DM gave the two (the wife especially) a buoyancy lesson. This was important, because the DM had chosen a site that had intricate channels through the coral. As we did the dive, it became obvious that even with that impromptu lesson, the dive was too advanced for that couple, and the DM ended up skipping a couple of nice looking channels. After the dive, he talked to them about their weighting (too much) and other things they needed to work on to make their diving more enjoyable.
But here's my point....
The DM did not realize this, but I had just certified my supposedly more advanced friends the day before. This was their first day diving after their OW certification.
It shows the tremendously wide range of what constitutes an advanced diver, and what constitutes an advanced dive. It also shows what it takes to become advanced. How many overweighted dives would that couple have to do in conditions that really didn't matter before their skills improved enough to be considered advanced? I submit that no number would be right. Doing a dive that raised the ante on their skills, and having a DM stop the dive and work with them on their skills did more to improve them than all their previous dives combined. Simply repeating the same basic dives over and over again will do nothing to move you to an advanced level of diving.