The short answer is, patriarchy is a dominance based social hierarchy that not only posits men as dominant predators who prey on "naturally" submissive women, it also justifies other types of social stratification maintained by coercion, violence, and the threat of violence. It is essential the root of all of our social ills, such as racism, homophobia, xenophobia, etc., as well as garden variety bullying.
Here's some more about that from me, but The Chalice and the Blade is an excellent, comprehensive resource.
"In other words, patriarchy is at its heart a dominance-based hierarchy where might makes right, and those who have the most social power have gotten it by intimidation, force, and coercion and by maintaining traditional power once it is established. This is typically accomplished by keeping those further down the pecking order from having an actual chance to compete. Ruthlessness is not only an accepted method of acquiring and maintaining power, but for many, it actually reads as a leadership quality, even today."
