əbˈseshən, äb- noun
( -s )
Etymology: Latin obsession-, obsessio, from obsessus (past participle of obsidēre to besiege) + -ion-, -io -ion
1. obsolete : siege
2. : the act of a devil or a spirit in besetting a person or impelling him to action from without : the fact of being so beset or impelled — distinguished from possession
3.
a. : a persistent and disturbing intrusion of or anxious and inescapable preoccupation with an idea or feeling especially if known to be unreasonable — compare compulsion
b. : an emotion or idea causing such intrusion