| Acronym | Definition |
|---|
| ACSI | Association of Christian Schools International |
| ACSI | American Customer Satisfaction Index |
| ACSI | Association Canadienne des Sciences de l'Information (French) |
| ACSI | Army Chief of Staff for Intelligence (US DoD) |
| ACSI | American Communications Services, Inc. (telecommunications company) |
| ACSI | Anglo-Chinese School (Independent) |
| ACSI | Atari Computer System Interface |
| ACSI | Appalachian Clean Streams Initiative |
| ACSI | Association of Clinical Scientists in Immunology (United Kingdom) |
| ACSI | Alcoa Closure Systems International (various locations) |
| ACSI | Antiguo Colegio de San Ildefonso (museum in Mexico City) |
| ACSI | Afghanistan Civil Service Institute |
| ACSI | Advanced Computer System Interface |
| ACSI | America's Counter-Smuggling Initiative |
| ACSI | Abstract Communications Service Interface |
| ACSI | Airport Certification Safety Inspector (FAA) |
| ACSI | Alcan Composites, Singen (European aluminum plant) |