The gender- and sex-essentialist belief system which states that men are inherently more dominant, powerful, aggressive, or ambitious than women. Usually accompanied by the parallel belief that women are inherently more submissive, weak, nurturing, or delicate than men.
Man: I want to have kids, but I fear I won't be as nurturing to them as their mother.
Women: Don't let the Testosterone Rex get to you, sex doesn't determine how nurturing you are!