| Acronym | Definition |
|---|
| MSec | Multicast Security |
| MSec | Millisecond |
| MSec | Mandrake Security |
| MSec | Medical Supplies & Equipment Company (various locations) |
| MSec | Myanmar Securities Exchange Centre (est. 1996; joint venture; Myanmar and Japan) |
| MSec | Message Security |
| MSec | Mathematical and Scientific E-Content |
| MSec | Mohamed Sathak Engineering College (India) |
| MSec | Mongolian Securities and Exchange Commission |
| MSec | Major and Special Events Committee (Worcester Polytechnic Institute) |
| MSec | Mountain State Employers Council |
| MSec | Mennonite Secondary Education Council |
| MSec | Master of Science in Economics |