• Sanitary sewer overflow
• Senior Station Officer, a rank in the New Zealand Fire Service
• Special Security Office, is a function of the US federal government and armed forces
• Special Security Officers, a group of people with law Enforcement
• Single sign-on, a system designed to minimize the number of times that a user must log into multiple applications
• Enterprise single sign-on
• Sso (rite), an initiation rite once practised by the Beti of Cameroon
• Standards Setting Organization, an organization promulgating or maintaining standards
• Starship Operators, a TV sci-fi anime series
• Sydney Star Observer, a newspaper in Sydney, Australia
• UMF/SSO-3 ASH, a battlesuit in the anime Gundam
• Iraqi Special Security Organization

In music:

• The Salford Symphony Orchestra
• Saskatoon Symphony Orchestra
• BBC Scottish Symphony Orchestra
• Seattle Symphony Orchestra
• Shreveport Symphony Orchestra
• Siding Spring Observatory
• Singapore Symphony Orchestra
• Springfield Symphony Orchestra
• Sudbury Symphony Orchestra
• Sydney Symphony
• Syracuse Symphony Orchestra

In spaceflight:

• Scaled Composites SpaceShipOne, the vehicle used in the first ever privately funded human spaceflight
• Semi-synchronous orbit, a type of Earth orbit
• single-stage-to-orbit, a vehicle that reaches orbit without jettisoning hardware
• Space Shuttle Orbiter, an orbital spaceplane operated by NASA
• Sun-synchronous orbit, a type of Earth orbit