Other
- Transportation security officer, a federal employee of the Transportation Security Administration, a division of the U. S. Department of Homeland Security
- Transaero Airlines (ICAO airline designator code)
- Tresco Heliport (IATA Airport Code)
- Total Shares Outstanding, a financial term referring to the stock held by investors, including restricted shares, as well as those held by the public
- Tourist Standard Open, a type of British Railways coach
- Marcos TSO, a sports car manufactured by Marcos Engineering Ltd.
Read more about this topic: TSO