Depends on what kind of definition you are looking for. In other words define 'definition'.
Masculine is an adjective, so you want the definition of a word that differentiates another word as distinct from something else (adjectives dont meet the rigor of a description).
So technically that would be a stipulative definition. Meaning that it has the meaning the speaker wants for the purpose of their discourse.
The context of your post puts the definition as something you are not.
So you answered your own question and your post fails the rigor test for philosophical questions.
{incoming rant}
It's pretty much impossible to logically and rigorously demonstrate that masculinity
should mean anything, have any effects, be valued by anyone, or be worth posting about on the internet. I think the closest thing you can say about this subject that is anywhere near rigorously true is this: A lot of guys think being gay isn't manly. They also think of being on the catching end of anal stimulation isn't manly. There's not really any reason why we can't all change our minds, although realistically it will take a few generations, if it ever happens.
The biological roots of why guys are like they are, when you look at them, aren't anywhere near as glorious as the old codgers try to make it sound as they sit on their porch yelling at people and complaining that we've all lost our way and don't know what it's like to be a man anymore. And everything that isn't biological is just cultural, a passing in the wind.
One day, I hope the general American public can have a discourse on this that makes more sense. At the moment it seems like you can't hear anyone in the middle, only those on the far sides -- like they either believe we should go back to not letting women have jobs, or we should abandon all forms of culture as meaningless and worthless. I don't think we have to be so nihilistic that we have to reject human suffering and joy as meaningless; given that, I think we could start to try and examine culture for what the different parts of it do, and thus to separate the wheat from the chaff.
I'm going to disagree with virtually everyone I've read on the subject and say that gender roles are based at least 95% in pure arbitrary culture, but also say that doesn't make them inherently bad. I think the fact that they can still be observed in existence is almost proof of their worth by itself.