| OR(S) | Odds Ratio(S) 
| Others |
| OR(s) | Operating Room(s)
| Others |
| ORS | Oakland Roadster Show
| Others |
| ORS | Object Relational Server
| Others |
| ORS | Obligated Reserve Service
| Others |
| ORS | Occupant Restraint System
| Others |
| ORS | Occupational Requirements Survey
| Others |
| ORS | Oculo-Respiratory Syndrome
| Others |
| ORS | Off Road Series
| Others |
| ORS | Off Road Shocks
| Others |
| ORS | Off Road Show
| Others |
| ORS | Off Road Solutions
| Others |
| ORS | Off Road Suspension
| Others |
| ORS | Off Road System
| Others |
| ORS | Offense Reporting System
| Others |
| ORS | Office for Research Safety
| Others |
| ORS | Office for Research Support
| Others |
| ORS | Office of Radiological Security
| Others |
| ORS | Office of Recovery Services
| Others |
| ORS | Office of Regulatory Science
| Others |
| ORS | Office of Regulatory Services
| Others |
| ORS | Office of Regulatory Staff
| Others |
| ORS | Office of Rehabilitation Services
| Others |
| ORS | Office of Research Security
| Others |
| ORS | Office of Research Services
| Others |
| ORS | Office of Research Support
| Others |
| ORS | Office of Retirement Services
| Others |
| ORS | Office Research Service
| Others |
| ORS | OID Resolution System
| Others |
| ORS | Oil Recovery System
| Others |
| ORS | Old Red Sandstone
| Others |
| ORS | Olfactory Reference Syndrome
| Others |
| ORS | On The Road To Success
| Others |
| ORS | One Room Schoolhouse
| Others |
| ORS | Ongoing Resourcing Scheme
| Others |
| ORS | Online Recovery Service
| Others |
| ORS | Online Registration System
| Others |
| ORS | Online Reporting System
| Others |
| ORS | Open Random and Supportive
| Others |
| ORS | Open Research System
| Others |
| ORS | Open Retail System
| Others |
| ORs | Operating Rooms
| Others |
| ORS | Operation Related Services
| Others |
| ORS | Operation Reporting System
| Others |
| ORS | Operational Research Society
| Others |
| ORS | Operationally Responsive Space
| Others |
| ORS | Opioid Response Strategy
| Others |
| ORS | Oracle Reports Services
| Others |
| ORS | Oral Rehydration Salt
| Others |
| ORS | Oral Rehydration Salts
| Others |
| ORS | Oral Rehydration Solution
| Others |
| ORS | Orally Rehydrating Solution
| Others |
| ORS | Orange Room Studios
| Others |
| ORS | Orbital Refueling System
| Others |
| ORS | Orcas Island Airport
| Others |
| ORS | Oregon Revised Statutes
| Others |
| ORS | Organic Reconstruction Syrum
| Others |
| ORS | Organic Root Stimulator
| Others |
| ORS | Organizational Role Stress
| Others |
| ORS | Orlando Riva Sound
| Others |
| ORS | Orpheus Island Resort, Queensland, Australia
| Others |
| ORS | Orroval Valley, Australia (Spaceflight Tracking and Data Network station)
| Others |
| ORS | Orthopaedic Research Society
| Others |
| ORS | Outer Rim Scouts
| Others |
| ORS | Output Record Separator
| Others |
| ORS | Outside Release Switch
| Others |
| ORS | Outsourced Recruiting Solutions
| Others |
| ORS | Ovarian Remnant Syndrome
| Others |
| ORS | Overseas Research Scholarship
| Others |
| ORS | Oxygen Recycling System
| Others |
| ORS | Oxygen Reduction System
| Others |