ob·ses·sive 
(əb-sĕsĭv, ŏb-)
(əb-sĕsĭv, ŏb-)adj.
1. Of, relating to, characteristic of, or causing an obsession: obsessive gambling.
2. Excessive in degree or nature: an obsessive need to win.
ob·sessive n.
ob·sessive·ly adv.
ob·sessive·ness n.