| Abbreviation | Definition |
|---|---|
| ACS | American Cancer Society |
| ACS | Association of Caribbean States |
| ACSE | Association for Computer Studies Educators |
| ACSEC | Atlantic Canada Sustainable Energy Coalition |
| ACSI | Association of Christian Schools International |
| ACSICTF | Association of Christian Schools International Children's Tuition Fund |
| ACSSP | American Council of Spanish Speaking People |
| ACSW | Academy of Certified Social Workers |
| ACT | Action Changes Things |
| ACT | Action For Nature |
| ACT | Advocates for Cultural Talk |
| ACT | Amazon Conservation Team |
| ACT | Association of Consumers and Taxpayers |
| ACTE | Association of Corporate Travel Executives |
| ACTF | ACSI Children's Tuition Fund |
| ACTL | A Child To Love |
| ACTM | Association of Certified Treasury Managers |
| ACTRA | Atlantic Canada Trail Riding Association |
| ACTS | A Coalition To Support |
| ACTS | Abundant Care Training Services |