Learn how to say Obsessional correctly in English with this tutorial pronunciation video.
Oxford dictionary definition of the word obsession:
the state of being obsessed with someone or something:
she cared for him with a devotion bordering on obsession
[count noun] an idea or thought that continually preoccupies or intrudes on a person’s mind:
he was in the grip of an obsession he was powerless to resist
early 16th century (in the sense ‘siege’): from Latin obsessio(n-), from the verb obsidere (see obsess)