IDEE FIXE is a French phrase meaning 'fixed idea' or 'OBSESSION'. It is used to describe an idea or thought that is held onto strongly and obsessively. FIXATION, MONOMANIA, and OBSESSION are all terms that can be used to describe IDEE FIXE. FIXATION is an intense and persistent focus on a single object or idea, while MONOMANIA is an excessive preoccupation with a single idea or subject. OBSESSION is an irrational and persistent focus on a single idea or object. All three terms can be used to describe IDEE FIXE.