| Acronym | Definition |
|---|
| TSEC | Top Secret |
| TSEC | Taiwan Stock Exchange Corporation |
| TSEC | Transmission Security |
| TSEC | The Solar Energy Consortium |
| TSEC | Thadomal Shahani Engineering College (Mumbai, India) |
| TSEC | Telecommunications Security |
| TSEC | Tissue-Selective Estrogen Complex |
| TSEC | Training Systems and Education Conference |
| TSEC | The Solid Energy Crew (Swedish internet music group since 1996) |
| TSEC | Technical Specification Evaluation Certificate |
| TSEC | Thermally Stimulated Electric Conductivity |
| TSEC | Transmission Secure |
| TSEC | Three Speed Ethernet Controller |
| TSEC | Tactical Speech Security Equipment |
| TSEC | Terminal Secondary Radar Beacon |
| TSEC | Telecommunications Systems Engineer Course |
| TSEC | Transmission Security Encryption Code |
| TSEC | Triangle South Enterprise Center (Dunn, NC) |
| TSEC | Technical Specification Evaluation Centre (Bangalore, India) |
| TSEC | Tertiary Student Enrolment and Completions |