An obsessive enthusiast is someone who is extremely passionate and devoted to a particular activity or interest. This type of person can be described as a MANIAC, NUT, or NERD. A MANIAC is someone who is driven by an intense and often uncontrollable enthusiasm, while a NUT is someone who is obsessed with something to the point of being considered eccentric. A NERD is someone who is highly knowledgeable and enthusiastic about a particular subject.