ob•ses•sivePronunciation: (ub-ses'iv), [key]
being, pertaining to, or resembling an obsession: an obsessive fear of illness.
causing an obsession.
excessive, esp. extremely so.
someone who has an obsession or obsessions; a person who thinks or behaves in an obsessive manner.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.