- oblivion: obscurity
- oblivious: inattentive or unmindful
- obscure: dark, vague, unclear
- obsequious: very attentive, fawning
- obsessive: related to thinking about something constantly;
- obstinate: stubborn, hard to control
- obtuse: blunt, stupid
- officious: meddlesome
- ominous: threatening
- provocative: arrousing anger or interest