Main Entry: ob·sess

Pronunciation: \əb-ˈses, äb-\

Function: verb

Etymology: Latin obsessus, past participle of obsidēre to frequent, besiege, from ob- against + sedēre to sit — more at ob-, sit

Date: 1531

transitive verb : to haunt or excessively preoccupy the mind of <was obsessed with the idea>intransitive verb : to engage in obsessive thinking : become obsessed with an idea