Cissexism is the belief that transgender and/or transsexual people are inferior to cisgender people or those who identify with the gender that was assigned to them at birth. Because the majority of the population is believed to be cisgender, trans people are a minority who may suffer discrimination and ill treatment as a result of their sexual identity.
More About Cissexism
Cissexism may be used as a synonym for transphobia, but it differs a bit. While transphobia refers to discomfort, disgust, fear, or anger directed at people who do not fit into society's gender expectations, cissexism is based on the assumption that there are only two genders (male and female), and that these genders are determined solely by biological sex. Cissexism often involves positioning cisgender as better or more "real" than trans identities.