According to the Free Dictionary by Farlex:
Acronym Definition
UST System Universal Tubeless (Mavic)
UST Ultra Sonic Testing
USt Umsatzsteuer (German: Tax)
UST Undergraduate Space Training
UST Underground Storage Tank
UST Unit Security Technician
UST United Sports Technologies
UST United States Treasury
UST United States Treaty
UST Universal Standard Time
UST Universal Systems and Technology, Inc.
UST University of Santo Tomas (Manila, Philippines)
UST University of Science & Technology (Yemen)
UST University of St. Thomas (Minnesota, Texas)
UST Unresolved Sexual Tension
UST Unstretched
UST Urbanna Swim Team (Manassas, Virginia)
UST User Status Table
UST Utah State Theatre