I was DVD shopping earlier today and was seeing the terms MAR and OAR used in the descriptions. Naturally the first place that I looked to for help was the videohelp glossary and What Is DVD section. After not having any luck I resorted to using Google and after a little digging found the definitions. I though it might be helpful to add them to the Glossary in case anyone in the future is curious.

MAR - Modified Aspect Ratio (Full Screen)
OAR - Original Aspect Ratio (Wide Screen)