| Abbreviation | Definition |
|---|---|
| OAHS | Oxfordshire Architectural and Historical Society |
| OAL | Outdoor Area Lighting |
| OAL | Outside Air Louver |
| OAM | Open Architecture Management |
| OAN | Open Architecture Network |
| OAW | Ottawa Architecture Week |
| OBC | Ontario Building Code |
| OBL | Oblique |
| OCA | Open Control Architecture |
| OCCS | Overall Construction Classification System |
| OCFA | Open Computer Forensics Architecture |
| OD | Outer Diameter |
| OD | Outside Dimension |
| ODAT | Ohio Design Assistance Team |
| OEOB | Old Executive Office Building |
| OESC | Ontario Electrical Safety Code |
| OFC | Ontario Fire Code |
| OFCH | Oil-Fired Central Heating |
| OFCI | Owner Furnished, Contractor Installed |
| OFL | Over-FLow alarm |