According to Osho, when male and female energies reach a fifty-fifty balance, their polarity neutralizes: the person becomes asexual/androgynous, steps out of the dialectics of sex, and reflects the neuter, impartial nature of Brahman (ardhanarishwara), both and neither. Biologically this can appear as the third sex; spiritually it signifies transcendence of gender duality, an inner wholeness that no longer seeks completion through the opposite.
When your inner masculine and feminine are perfectly even, the push-pull of sex ends and you become neutral and whole, not chasing an opposite.