A belief or argument that male-female sexuality is the only natural or moral mode of sexual behavior. Also, incidentally, the effects of that cultural ideology. The word 'heterosexualism' has also been proposed to mean essentially the same thing. [see reference 1]
This word has been suggested as alternative to homophobia [see reference 2], in part because it uses a parallel structure to sexism or racism. This parallel approach, however, is logically flawed, as the literal meaning of the word would therefore be "a belief that one type of heterosexuality is inherently 'better' than another type of heterosexuality" (see the dictionary definition of, for example, racism). A true parallel construction can be found in the word sexualism.
Heterosexism should not be confused with the more semantically precise heterocentrism, which is an (often subconscious) assumption that everyone is heterosexual, and the attitudes associated with that assumption.
In queer theory, the term heterocentrism is closely related to heteronormativity.
Sources
[1] Corsini, Raymond J., The Dictionary of Psychology (2001), ISBN 1583913289
[2] Herek, Gregory M., Ph.D., " Beyond 'Homophobia': Thinking About Sexual Prejudice and Stigma in the Twenty-First Century." Sexuality Research & Social Policy (April, 2004)
See also
homophilia, homophobia, homosexuality, anthrophobia , heterosexualism, sexualism, heterocentrism, heteronormativity