My understanding of masculinity is that it refers to behaviour that is constructed by and serves to maintain male dominance.  Masculinity is not just that which pertains to men, since men can be seen, and consider themselves, to be insufficiently masculine… Masculinity is not, then, a biological fact, something connected with particular hormones or genes.  Masculine behaviour or appearance or artifacts, and design, signify ‘manhood’ as a political, not a biological, category.  In this understanding masculinity cannot exist without its supposed opposite, femininity, which pertains to female subordination. Neither masculinity nor femininity make sense or can exist without the other as a reference point.

–Sheila Jeffreys, Unpacking Queer Politics