obsessionEnglishOxford English Thesaurusobsession noun the idea grew in his mind until it became an obsession: fixation, ruling/consuming passion, passion, mania, idée fixe, compulsion, preoccupation, enthusiasm, infatuation, addiction, fetish, craze, hobby horse; phobia, complex, neurosis; informal bee in one's bonnet, hang-up, thing, bug.obsession Oxford Dictionary of English