group resulting from social constructs have grant less power or representation compared to other members or groups in society; acts as a contrast to underrepresented minority (URM)
When using any term for a group, it's important to contextualise it into people. So, for example, "people from the overrepresented majority are less likely to be affected by this change" over "the overrepresented majority are less likely to be affected by this change."
As the underrepresented minority (URM) is the more commonly used term, it has an impact of focusing issues on that that group, which often can imply and place the burden of fixing the problem is onto that group. Underrepresented can imply that the group can do more to represent themselves.
Meanwhile, the overrepresented majority is usually the group that possesses the power to influence which groups are majoritised (and subsequently receive power) and which groups are minoritised. It renders this power dynamic invisible.
Naming the overrepresented majority allows us to discuss the power dynamic involved, and places emphasis on the fact that it's not about minoritised groups being underrepresented, but that it is also about majoritised groups being overrepresented.
It also allows prevents the false dichotomy where everyone is either "default/unnamed" or from an underrepresented minority. Without it, people from underrepresented minorities are forced to carry a label when people from overrepresented majorities are not.
The term overrepresented majority allows us to discuss the holistic systems and all of the players involved.