| Abbreviation | Definition |
|---|---|
| OPR | Oxygen Pressure Regulator |
| OPRV | Oxygen Pressure Relief Valve |
| OPS | OPerational Sequence |
| OPS | Orbiter Project Schedule |
| OPS | Oxygen Purge System |
| OPSB | Orbiter Processing Support Building |
| OPSR | OPerations SupervisoR |
| OPSS | Orbital Propellant Storage Subsystem |
| OPT | Operational Pressure Transducer |
| OPT | Optics |
| OPT | Optimum |
| OPT | Option |
| OPT | Ozone Processing Team |
| OPTB | Operational Program Time Base |
| OPTB | Operator Proficiency Training Board |
| OPWS | Orbiter Payload Work Station |
| OQA | Office of Quality Assurance |
| OQC | Office of Quality Control |
| OQI | Organizational Quality Improvement |
| OQT | Operational Qualification Testing |