Defeminization is a term in developmental biology

Biology

Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is a vast subject containing many subdivisions, topics, and disciplines...

, especially zoology

Zoology

Zoology |zoölogy]]), is the branch of biology that relates to the animal kingdom, including the structure, embryology, evolution, classification, habits, and distribution of all animals, both living and extinct...

, referring to an aspect of the process of sexual differentiation

Sexual differentiation

Sexual differentiation is the process of development of the differences between males and females from an undifferentiated zygote...

 by which a potential female-specific structure, function, or behavior is prevented from developing by one of the processes of male development. Although the term might seem to imply "removal" of female characteristics, in nearly all biological contexts it refers to prevention of an aspect of female development from manifesting.

In human biology of gender

Biology of gender

Biology of gender can have different meanings, depending on the meaning of gender.* In medicine and biology it usually refers to the biology of sexual dimorphism, e.g...

, the best known example of this is the prevention of development of the müllerian duct

Müllerian duct

Müllerian ducts are paired ducts of the embryo that run down the lateral sides of the urogenital ridge and terminate at the Müllerian eminence in the primitive urogenital sinus. In the female, they will develop to form the Fallopian tubes, uterus, cervix, and the upper two-third of the vagina; in...

 derivatives by anti-müllerian hormone

Anti-müllerian hormone

Anti-Müllerian hormone also known as AMH is a protein that, in humans, is encoded by the AMH gene. It inhibits the development of the Müllerian ducts in the male embryo. It has also been called Müllerian inhibiting factor , Müllerian-inhibiting hormone , and Müllerian-inhibiting substance...

 (AMH) in the 3rd and 4th months of fetal

Fetus

A fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization.-Etymology and spelling variations:The...

 development, though the term is not commonly used in discussions of human development.

In a number of non-human mammal

Mammal

Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

s, there is evidence that hormones produced by the testes act directly on the brain

Brain

The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...

 to prevent development of female characteristics, especially female reproductive behavior.