This Act may be cited as the Defining Male and Female Act of 2025.

Chapter 1 of title 1, United States Code, is amended by adding at the end the following: 9. Definition of sex, male, female, and related terms In determining the meaning of any Act of Congress, or of any ruling, regulation, or interpretation of the various departments and Federal agencies of the United States, the term— (1) boy means a minor human male; (2) father means a male parent; (3) female, when used to refer to a natural person, means a person belonging, at conception, to the sex characterized by a reproductive system with the biological function of producing eggs (ova); (4) gender identity means an identity that reflects an internal and subjective sense of self, disconnected from biological reality and sex and existing on an indeterminate continuum, and, because such an identity does not provide a meaningful basis for identification for purposes of Federal law, the term shall not be recognized by the Federal Government as a replacement for sex; (5) girl means a minor human female; (6) male, when used to refer to a natural person, means a person belonging, at conception, to the biological sex characterized by a reproductive system with the biological function of producing sperm; (7) man, except when used as a generic reference to human beings, means an adult human male; (8) mother means a female parent; (9) sex, when referring to a natural person's individual’s sex, means the person’s immutable biological classification as either male or female, as biologically determined and defined by this section; and (10) woman means an adult human female..