Common meaning:

It is typical for a person’s gender identity and biological sex to be in accord with one another.

Hidden meaning of the Equity religion: 

The social expectation that excludes gender non-conforming identities. It is considered systemic oppression against trans people since it props up normal gender expectations.

Discussion:

According to the Equity faith the very concept of normal gender expectations is damaging and oppressive and must be attacked. Expecting people to have their gender idenity and biological sex match is a weight around the neck of non-conforming gender identity persons.

Cisnormativity is a new pejorative word that has been invented in order to allow Equity believers to attack everyone who says they have a normal gender. The Equityists can then claim that this new imaginary group of people is harming the non-conforming gender group.   

From the Equity perspective, the dominance of cisnormativity needs to be challenged because of all the harm it creates. Everyone needs to be free to be the gender they really are.

The truth is that the Equityists want to eliminate every oppressor group they identify and this includes the normal gender group.  They pretend that for gender, all they want is equality and fairness, but they are actually aiming for outright destruction of normally gendered people.