You just can't get more masculine than a bull. (At least, according to the Egyptians, Mesopotamians, and the peoples of the Indus Valley. So, it's no surprise that Gilgamesh is described as "the hero […] the goring wild bull" (1.29). The image of a bull comes up a lot, and when it does, it means masculinity, power, and violence.
When Gilgamesh and Enkidu are on their way to the Cedar Forest, Gilgamesh has a rather scary dream where he encounters a bull that splits the ground with his breath. Enkidu interprets this dream as meaning that Shamash will help them defeat Humbaba, but, you know what? We're going say that it's probably an omen that the Bull of Heaven will be their next opponent.
We think it's more than a coincidence that Gilgamesh is referred to as a "Bull" and then gets the divine stink-eye when Enkidu kills "The Bull of Heaven." What does it all mean? Well, of course, we see Gilgamesh as the supreme masculine character: he's an epic hero with all the good looks, incredible strength, unwavering determination, and all that other tasty stuff. And, just maybe, the Bull of Heaven represents the masculinity, power, and violence of the gods.
So, is Enkidu essentially demonstrating the superior power and masculinity of humanity when he slaughters that Heavenly Bull? We leave it to you to decide.