| Acronym | Definition |
|---|
| NAO | North Atlantic Oscillation |
| NAO | National Audit Office (UK government) |
| NAO | Not an Option |
| NAO | National Astronomical Observatory (Japan) |
| NAO | Négociation Annuelle Obligatoire (French: Mandatory Annual Negotiation) |
| NAO | National Applications Office (US DHS) |
| NAO | New Account Opening (various companies) |
| NAO | North American Operations |
| NAO | non-asbestos organic |
| NAO | National Academy of Opticianry |
| NAO | New Age Outlaws (wrestling) |
| NAO | National Authorising Officer (various nations) |
| NAO | National AHEC (Area Health Education Center) Organization |
| NAO | Sodium Oxide |
| NAO | New Anzat Order (Star Wars) |
| NAO | Natural Atomic Orbital |
| NAO | Native American Outreach |
| NAO | Naval Aviation Observer |
| NAO | Non-Animal Origin |
| NAO | Nasal Airway Obstruction |
| NAO | Number Allocation Organisation |
| NAO | New Associate Orientation (introductory training for new employees) |