A source of energy in males which is the equivalent of passion or "life force," and which is more than just a "style" of behavior. It is inborn, an instinct, not learned. It is the same as "passion," but not in any vague sense of the word.
Masculinity is male passion specifically coded as an inborn set of instincts that unconsciously guide those who have it, to successfully reproduce, and to survive in general, with specific instincts that feed the male soul and are attuned to its identity.
Romantic Dynamics extends these two genetic prime directives into the modern day context to mean, "automatic romantic instincts of sexual attraction," and gender-based instincts that when seen in unconscious, automatic behaviors, lead the individual to feel immediately "more alive," excited, "full of life," (as seen in modern consumer purchasing behavior.)
This is not to say that one's sense of "spiritual purpose" is left out of the experience of masculinity. It is simultaneously logical to conclude that the two Darwinian/Freudian scientific principles above, govern it, but masculinity also gives a person possessing it, a core feature of the "sense of self," or identity.
In spiritual terms, it is the "god principle within." So, masculinity is revealed in its subtleties in the form of the instincts of the gods in the ancient myths and Greek plays.
It is very energetic and is amplified by some very specific things like ownership of resources, education and technology, privacy, leadership, fighting and winning, and rather than an “inner giving birth to,” an “outer creativity” that centers on the targeted goal-seeking that men tend to call “having a mission” - all gender instincts highlighted by stories of the Greek gods.
It is the opposite of drawing on sociology or the mere "opinion" of others, "gender-roles" that can shift or change, and it has synonyms in instinct, passion, and sexiness.
It doesn't matter if it is felt by those who are attracted to the same gender or opposite gender, so long as one's core identity identifies with it.
Then, in purely romantic terms, when it is expressed to others with femininity or a feminine identity, it amplifies that identity in them, and sexually attracts them in so doing.
Likewise, when expressed to those who also have masculinity, it amplifies itself in them through gender-affinity based friendship and collegiality that one could call "brotherhood," or a profoundly deep automatic, instinctual friendship felt by kin.
Expressing masculinity makes one more powerful and alive, then, while also making the recipient more powerful and alive.