I'm not sure how to describe masculinity. It's a certain energy, maybe. I'm thinking of the saying "he's secure in his masculinity." This guy is impressive because he knows who he is. He doesn't need outward validation. Other people's standards of masculinity don't concern him.
Once I got over what other people thought about me, I started dressing and moving about in the world in ways that feel right for me. These days, I'm secure enough in my masculinity that I don't feel the need to prove it to anyone else. I am who I am, and I feel great about it.