Definition for Heterosexism
From Biology Forums Dictionary
Heterosexism is a system of attitudes, bias, and discrimination in favor of opposite-sex sexuality and relationships. It can include the presumption that other people are heterosexual or that opposite-sex attractions and relationships are the only norm and therefore superior.
Heterosexism as discrimination ranks gay men, lesbians, bisexuals and other sexual minorities as second-class citizens with regard to various legal and civil rights, economic opportunities, and social equality in many of the world's jurisdictions and societies. Heterosexism is often related to homophobia.