| Abbreviation | Definition |
|---|---|
| ACRU | American Constitutional Rights Union |
| ACRW | American Council of Railroad Women |
| ACSEF | Australasian Coal Shale Employees Federation |
| ACSEF | Australasian Coal & Shale Employees Federation |
| ACSU | Addison Central Supervisory Union |
| ACTA | Assam College Teachers Association |
| ACTRA | Alliance of Canadian Television and Radio Artists |
| ACTU | Australian Caucus for Trade Unions |
| ACTU | Australian Council of Trade Unions |
| ACU | Alabama Credit Union |
| ACU | Allegiance Credit Union |
| ACU | American Cuck Union |
| ACU | America's Credit Union |
| ACU | Asian Currency Union |
| ACU | Associated Credit Union |
| ACU | Credit Union |
| ACUB | Alma College Union Board |
| ACUF | American Conservative Union Foundation |
| ACUI | Association of College Unions International |
| ADCU | Additional Deduction for Credit Unions |