Masculinity (n.) is the libido itself. Femininity begins in masculinity but diverges from it.
Masculinity (n.) and femininity usually just mean active and passive — a poor equation, since a nursing mother is active, female spiders are the stronger, and men need passivity to live together.
Masculinity (n.) is a lazy label in psychology: we call whatever is strong and active male, whatever is weak and passive female, and know the equation is inadequate.
Masculinity (n.) and femininity have no psychological meaning until they fuse with active and passive — and even then the coupling is less complete than we assume.
Masculinity (n.) and femininity are concepts psychoanalysis takes over without explaining; pressed, they dissolve into activity and passivity.
Masculinity (n.) and femininity are theoretical constructions when pure; everyone mixes the traits of both.