We all know that a tourist can stay in Morocco for up to 90 days. But it is not clear whether that means 90 days PER VISIT or 90 days total per year,etc.

This is not spelled out by Moroccan law or policy because most "tourists" are not going to visit Morocco or any other country for 90 days on one visit and then repeat this process 2, 3, or 4 times annually because it makes no sense. If you want to spend that much time in Morocco in one year, then you need to discuss your intentions with Moroccan authorities and apply for residency status which would allow you to spend up to 6 months in Morocco at one time. Then you can leave for a brief period of at least 48 hours and return for another 6 months if you choose, as long as your reasons for wanting to spend that much there are up-front and honorable.

It's pretty clear that a tourist can stay in Morocco for up to 90 days, but it's not clear whether that means 90 days PER VISIT or 90 days total per year, etc.

This is most likely not spelled out by Moroccan law or policy because most "tourists" are generally not going to visit Morocco or any other country for 90 days on one visit and then repeat this process 2, 3, or 4 times annually. If you wish to spend that much time in Morocco in one year, then I would suggest discussing your intentions with Moroccan authorities and looking into applying for residency status which may allow you to spend up to 6 months in Morocco at one time. Then perhaps you can leave for a brief period of time and return for another 6 months, as long as your reasons for wanting to spend that much there are up-front and honorable.