Contentious, a.
Etymology: [L. contentiosus: cf. F. contentieux.]
1. Fond of contention; given to angry debate; provoking dispute or contention; quarrelsome. Despotic and contentious temper. Macaulay.
2. Relating to contention or strife; involving or characterized by contention. Spenser. More cheerfull; though not less contentious, regions. Brougham.
3. (Law)
Contested; litigated; litigious; having power to decide controversy. Contentious jurisdiction (Eng. Eccl. Law), jurisdiction over matters in controversy between parties, in contradistinction to voluntary jurisdiction, or that exercised upon matters not opposed or controverted.
1 more senses
Syn. -- Quarrelsome; pugnacious; dissentious; wrangling; litigious; perverse; peevish. - Con*ten"tious*ly, adv. -- Con*ten"tious*ness, n.
Shades of meaning
Fernald lists contentious only as an antonym, under friendly.
He lists it without comment; the entries above explain its neighbors.