| Mississippi Affordable College Savings | Academic & Science |
| Member of the American Chemical Society | Academic & Science |
| Mobile Air Conditioning Society | Business |
| Magnetic Cell Separation | Chemistry |
| Micro and Anophthalmic Children's Society | Community |
| Minnesota Association of Christian Schools | Community |
| Mobility and Access Committee for Scotland | Community |
| Mecklenburg Area Catholic Schools | Community |
| Maryland Association of Community Services | Community |
| Macros | Computing |
| Microsoft Audit Collection Services | Computing |
| Monitor And Control System | Computing |
| Motorola Advanced Computer System | Computing |
| Master Active Control Station | Earth Science |
| Molecular and Cellular Sciences | Educational Degree |
| Modular Approach to Cloud Security | General |
| Macaroni and Cheese Shop | General |
| Maximum Adjacent Cut Specification | General |
| Modifiable And Combinable Securities | General |
| Multimedia Archive and Communication System | General |
| Magnetic Activated Cell Sorting | General |
| Minimal Access Cranian Suspension | General |
| Multi Axis Crystal | General |
| Manual Ability Classification System | General |
| Multi Axis Crystal Spectrometer | General |
| Manufacturing Automation and Control Systems | General |
| Morning Alcohol Confusion Syndrome | General |
| Manufacturers Assistance and Communications Staff | Governmental |
| Master-at-arms Senior Chief Petty Officer | Governmental |
| Manipur State AIDS Control Society | Manipur Government |
| Migration Analysis Cleansing Service | Medical |
| Minimal Access Cancer Surgery | Medical |
| Multicenter Aids Cohort Study | Medical |
| Multi Aids Cohort Study | Medical |
| Minimal Access Cranial Suspension | Medical |
| Maroondah Approach to Clinical Services | Medical |
| Mobile Armored Crew Station | Military and Defence |
| Modular Artillery Charge System | Military and Defence |
| Modular Artillery Charge System (artillery) | Military and Defence |
| Military Air Command Series | Military and Defence |
| Modem Access Control System | Networking |
| Multi-access Communication Server | Networking |
| Michigan Amateur Communications System | Radio Science |
| Modular Attitude Control System | Space Science |
| Mid-atlantic Championship Series | Sports |
| Martial Arts Collective Society | Sports |
