Tri-State Transit Authority, a transit service in the Huntington, West Virginia area

Tiny Toon Adventures

Time-Triggered Architecture, software architecture industry standard for distributed embedded real-time systems

Transport triggered architecture, a customizable processor architecture template

Terran Trade Authority, a science-fiction universe

TTA (codec), True Audio codec

Tibial tuberosity advancement, a knee operation in dogs

Teacher Training Agency - former name of the Training and Development Agency for Schools

Telefon Tel Aviv, an IDM band from the United States

Tennessee Telecommunications Association, a telecommunications industry trade organization

Texas Telephone Association, a trade association for telephone companies in Texas

The Tough Alliance, a synthpop duo from Sweden

Tomorrowland Transit Authority, a ride at Walt Disney World

Triangle Transit Authority, a regional transit service in North Carolina

Transport Ticketing Authority, a division of the Department of Infrastructure in the State Government of Victoria, Australia.