Common meaning:

Subject that considers the gender roles of men and women in society.

Hidden meaning of the Equity religion: 

Subject that tries to prove that biological sex is not real.

Discussion:

The Equityists believe that biology is not real and therefore biological sex or gender is not real. Gender studies assumes gender is totally socially constructed and discusses at length an ever growing number of genders.

Since Equity believers already know there is no biological difference between men and women, this leaves gender studies free to look for as many as it wants. At this point, the list of genders is over a hundred, each of which is created by subjective feelings of people, not any objective factual evidence.

In a gender studies course, the Equityists spend no time talking about how typical men and women behave, except to say how terrible and oppressive the two traditional genders are. All the rest of the time is spent exploring a fantasy land of genders that have no grounding in the real world.

When you ignore reality, bad things happen.