Definition of obsessor in US English:

obsessor

noun

rare
  • A person who behaves in an obsessive manner.

Origin

Mid 17th century (in an earlier sense). In sense 1 probably from classical Latin obsessor a person who takes possession of from obsess-, past participial stem of obsidēre + -or.

Pronunciation

obsessor

/ɒbˈsɛsə/