| Acronym | Definition |
|---|
| RSO | Rick Simpson Oil (cannabis oil extraction) |
| RSO | Radiation Safety Officer |
| RSO | Radio-Sinfonie-Orchester (German: Radio Symphony Orchestra) |
| RSO | Registered Student Organization (various universities) |
| RSO | Registered Sex Offender |
| RSO | Range Safety Officer |
| RSO | Remote Shared Object |
| RSO | Rapid Scan Operation |
| RSO | Remote Spool Output |
| RSO | Recognized Service Organization (Lutheran Church Missouri Synod) |
| RSO | Research Services Office (various locations) |
| RSO | Regional Security Officer |
| RSO | Recognized Student Organization |
| RSO | Roanoke Symphony Orchestra (Roanoke, VA) |
| RSO | Rent Stabilization Ordinance (housing) |
| RSO | Reactive search optimization (evolutionary computing technique) |
| RSO | Retirement Services Officer |
| RSO | Recognized Security Organization (International Maritime Organization ISPS code) |
| RSO | Road Safety Officer (Australia) |
| RSO | Robert Stigwood Organization |
| RSO | Research and Statistics Office (various locations) |
| RSO | Regina Symphony Orchestra (Canada) |
| RSO | Reconnaissance Systems Officer |
| RSO | Reduced Sign-On |
| RSO | Robotic Service Orchestration (various companies) |
| RSO | Regional Sales Office |
| RSO | Rainbow Symphony Orchestra (Paris, France) |
| RSO | Recovery Server Option |
| RSO | Ralstonia Solanacearum |
| RSO | Resident Space Object |
| RSO | Radiological Safety Officer |
| RSO | Repeat Sex Offenders (band) |
| RSO | Rohingya Solidarity Organization (Burma) |
| RSO | Regional Science Olympiad (education) |
| RSO | Regimental Supply Officer (US Navy) |
| RSO | Republic South Ossetia |
| RSO | Regimental Signals Officer (UK) |
| RSO | Registered Safety Officer (International Board of Environmental Health and Safety) |
| RSO | Religious Support Office |
| RSO | Rally Sport Ontario |
| RSO | Riverside County Sheriff's Office (California) |
| RSO | Remote Sales Officer |
| RSO | Rapid Scan Operation (GOES satellite) |
| RSO | Railway Sub - Office |
| RSO | Retail Sales Officer |
| RSO | Regional Supply Office |
| RSO | Rainbow Service Organization (Peterborough, ON, Canada gay rights and information) |
| RSO | Rogers Sportsnet Ontario (Canadian TV station) |
| RSO | Refined Soybean Oil |
| RSO | Resident Surgical Officer |
| RSO | Rough Stud Opening (construction) |
| RSO | Ridgewood Symphony Orchestra (Ridgewood, NJ) |
| RSO | Remote Split Operations (military UAVs) |
| RSO | Radiology Services Online (Celina, TX) |
| RSO | Regional Service Officer |
| RSO | Railway Sorting Office |
| RSO | Rechargement et Soudure de l'Ouest (French welding company) |
| RSO | Reconnaissance & Survey Officer |
| RSO | Remote Service Object |
| RSO | Right Salpingoophorectomy |
| RSO | Repeated Spike Oxidation |
| RSO | Revised Statute of Ontario (Canada) |
| RSO | Reservoir Surveillance Operations |
| RSO | Reported Significant Observation |
| RSO | Runway Supervisory Officer |
| RSO | Re-Entry Systems Operation |
| RSO | Registered Student Organisation |
| RSO | Reusable Software Object |
| RSO | ROKA Staff Office |
| RSO | Ravenna String Orchestra (Ravenna, OH) |
| RSO | Reserve Supplement Officer |
| RSO | Reconnaissance Staff Officer |
| RSO | Ron Smolen Orchestra (Chicago, IL) |
| RSO | Relationship Service Officer (finance; various organizations) |
| RSO | Red Saber Order (gaming) |
| RSO | Regional Standards Organization |
| RSO | Road Service Outfit (bright yellow motorbike and sidecar used by AA patrols up until the 1960's) |
| RSO | Rural Sub - Office |
| RSO | Requirements Staff Officer (US DoD) |
| RSO | Reservation Service Officer |
| RSO | Removal Services Overseas |
| RSO | Return Sales Order |