There are four meanings listed in oed's entry for the noun obsession, one of which is labelled obsolete. See ‘meaning & use’ for definitions, usage, and quotation evidence. Definition of obsession noun from the oxford advanced learner's dictionary.

A pattern of unwanted or intrusive thoughts or urges that recur persistently, often accompanied by symptoms of anxiety. A compulsive, often unreasonable idea or emotion. American heritage® … This absence of love, she argues, stems from an overwhelming obsession with the self, and from an excessive preoccupation with consumerism and material acquisition. The domination of one's thoughts or feelings by a persistent idea, image, desire, etc. See examples of obsession used in a sentence. The meaning of obsession is a persistent disturbing preoccupation with an often unreasonable idea or feeling;

The domination of one's thoughts or feelings by a persistent idea, image, desire, etc. See examples of obsession used in a sentence. The meaning of obsession is a persistent disturbing preoccupation with an often unreasonable idea or feeling; Compelling motivation. How to use obsession in a sentence.