Compulsory Heterosexuality refers to the idea that heterosexuality, as a default sexual orientation, can be adopted by people regardless of their personal sexual preferences. Compulsory means “mandatory”, “obligatory”, or “required”. A person’s heterosexuality is generally assumed until proven otherwise; by both one’s self and those around her. Those who have never “thought about” or questioned their heterosexual orientation may be accused of “compulsory heterosexuality”. Since heterosexuality is integral to the way a society is organized, it becomes a naturalized “learned behavior”. When a woman decides she is a lesbian (if this “deciding” even occurs), she is rejecting the ‘compulsion’ toward a heterosexual lifestyle and orientation. But Compulsory Heterosexuality makes coming out difficult, because it keeps women from being able to separate their “true sexual desires” from their “compulsions toward heterosexualty”. This is a concept that stems from the question of whether or not “anyone” could be a lesbian, and what agency an individual has over her sexual choices and desires.
As far as I know, this term was made popular by Adrienne Rich in her essay “Compulsory Heterosexuality and Lesbian Existence”, which is a critique of heterosexuality as an institution and it’s negative affects on women. Rich suggests that heterosexuality keeps women from actualizing their full sexual and emotional capacities by denying them a sexual way of being that is unrelated to male pleasure.
A Feminist Theory Dictionary 