My answer: It doesn't have a 'definition' because Manhood ultimately has a metaphysical explanation.
I regard manhood as dating back eternally; a matter of fundamental existence - and the same applies to womanhood.
In other words, sexual difference is a primal reality.
Reality began with a multitude of distinct entities, from which humans were 'made', and these were either male or female - one or the other.
Each of us was an independent eternal essence, even before we
were made Sons and Daughters of God. And this is the basis of agency or
'free will' - because there is something in us that did not come from
(And intermediate or combined or ambiguous sexual states are not fundamental but biological, metaphysically superficial. Although we do not necessarily or usually know the specific causes - we must presume that they have the same kind of pathological origins as other illness states: e.g. genetic, infective, toxic, neoplastic, traumatic and so on. Human physical and psychological development is an exceedingly complex process, and many things can - and do - go wrong at many or several stages. But metaphysically, in the soul; each person is either man or woman.)
The ultimate basis of reality is therefore dyadic; male and female; in a universe that is pluralistic - cannot be reduced to a single-entity unity.
The two sexes are not equal but strictly complementary - i.e. different and inter-dependent. Both are necessary. 'Man' is the combination of man and woman; but not a fusion, not an existential unity - rather as an irreducible duality bound by a relationship of love.