Defining masculine

Quick! Define "masculine". What makes a man masculine? It seems like it should be pretty simple: "masculine" means having the qualities of a man! So a "masculine man" is a man who has the qualities of a… man? That definition seems kinda circular, and probably not very, uh, useful. Get more specific, maybe? What qualities? Broad chin and shoulders, muscular, rough, tough, aggressive, strong, fit, leadership, sports, fighting, fearlessness, bravery, emotions limited to anger and pride, something about steaks and expensive cars(?)… The universal signs of manhood!

So there you go: all men exhibit those signs of manhood. Well, no, not all men: Some men don't have all or even most of those qualities, so I guess some men aren't masculine. Wait, that can't be right: masculine is supposed to mean "having the qualities of a man", so surely, by definition, every man has "the qualities of a man"?

Like, a man can be more, or less, masculine? But… how can a man be less, um, man?

Maybe those "masculine" features are supposed to be the ideal? An aspirational concept? Since I am a man, I should try to be more masculine? Should that be my goal because I am a man? Can I change my facial features? Can I change my personality? Should I lift weights for an hour a day? Why should I? What if I feel I am "manly" enough? What if those aren't my goals? Should I feel less masculine because I don't care to increase those arbitrary qualities? Who decided those traits are better, more masculine?

Could it be that "masculine" and "manly" are not very useful concepts?

(Homework: repeat the above exercise with "feminine".)