obsessive (obsessives plural )
1 adj If someone's behaviour is obsessive, they cannot stop doing a particular thing or behaving in a particular way.
oft ADJ about n
Williams is obsessive about motor racing...
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obsessively adv ADV with v, ADV adj
He couldn't help worrying obsessively about what would happen..., The Ministry is being obsessively secretive about the issue.
2 n-count An obsessive is someone who is obsessive about something or who behaves in an obsessive way. I am not an obsessive. Not at all.
obsessive-compulsive disorder
If someone suffers from obsessive-compulsive disorder, they cannot stop doing a particular thing, for example washing their hands. n-uncount