WordWeb Online

1. Inclined or showing an inclination to dispute or disagree, even to engage in law suits
   "a style described as abrasive and contentious";
   - combative, disputatious, disputative, litigious
    
2. Involving or likely to cause controversy
   "a central and contentious element of the book"

See also: adversarial, argumentative, controversial

Encyclopedia: Contentious