Sexism
Discrimination against women and sexual minorities, primarily by men.
On the Korean translation
“Sexism” is often translated into Korean as 성차별주의, but I think this is a mistranslation. The English suffix “-ism” can mean an ideology, but it can also mean discriminatory thinking. In “Feminism,” “-ism” denotes a philosophical position, so it should be translated as 여성주의. In “sexism,” however, it only means discriminatory thinking, so there is no need to translate it as 성차별주의; just 성차별 (sex discrimination) will do. Why dignify something like sex discrimination with an “ideology”?
The same applies to “racism” and “ageism”: not 인종차별주의 or 연령차별주의, but simply racial discrimination and age discrimination.