Definitions of contentious:

• adjective:   involving or likely to cause controversy

  Example: "A central and contentious element of the book- Tim W.Ferfuson"

• adjective:   inclined or showing an inclination to dispute or disagree, even to engage in law suits

  Example: "A style described as abrasive and contentious"

• adjective:   having or showing a ready disposition to fight

  Example: "A contentious nature"