APA Dictionary of Psychology

n. the systemic or interpersonal prejudice, discrimination, or bias that privileges cisgender people and devalues, invalidates, or marginalizes transgender and nonbinary or gender-expansive identities. Cissexism is based on the assumption that identifying with the sex assigned at birth (cisgender) is the norm, and that transgender or gender-expansive identities are abnormal. Cissexism can be explicit or implicit, and it can be perpetuated by individuals, institutions, and/or societal structures. See homophobia.