TSO

Science and technology

Technical Standard Order, a minimum performance standard issued by the FAA for certain items used on civil aircraft
Transmission system operator, an entity involved in electric power transmission or transmission of natural gas
Trichuris suis, a species of whipworm, a parasite of pigs

TCP segmentation offloading, a technique for increasing outbound throughput of high-bandwidth network connections
Time Sharing Option, an interactive command line interpreter for IBM mainframe operating systems OS/360, SVS, MVS, OS/390 and z/OS
Total store order, in microprocessor memory ordering

Transaero Airlines (ICAO airline designator code), a former Russian airline
Tresco Heliport (IATA airport code), a former heliport in the Scilly islands
Tourist Standard Open, a type of British Railways loco-hauled coach
Trailer Standard Open, a type of British Railways coach
Marcos TSO, a sports car manufactured by Marcos Engineering Ltd
Transportation security officer, a federal employee of the Transportation Security Administration, a division of the U. S. Department of Homeland Security

Threefold social order, a sociological theory involving the relationship of economy, polity and culture
The Sims Online, a massively multiplayer game
The Stationery Office, a British publisher
Total shares outstanding, the stock held by investors, including restricted shares, as well as those held by the public; see shares outstanding