Definition of "heterosexism"

heterosexism

noun
countable and uncountable, plural heterosexisms
1. The assumption made when relating to others that everyone is heterosexual.
  Quotations
  One of the driving forces behind slash and femslash is the pervading heterosexism of commercial media – if television will not give us the due proportion of same-sex eroticism we are entitled to expect, then we will make it for ourselves.
  2010, Stacey Abbott, The Cult TV Book, page 245
2. Discrimination or prejudice in favor of heterosexuals.