| Acronym | Definition |
|---|
| ACK | Acknowledge/Acknowledgement/Acknowledged |
| ACK | Amar Chitra Katha (Indian entertainment company) |
| ACK | Akademickie Centrum Kultury (Polish: Academic Center for Culture; Lublin, Poland) |
| ACK | Arbeitsgemeinschaft Christlicher Kirchen (German: Council of Christian Churches) |
| ACK | Audio Connection Kit |
| ACK | Ac Adaptor Kit |
| ACK | Acknowledgement |
| ACK | Automatic Color Killer |
| ACK | Acknowledgement Packet |
| ACK | Acknowledge Character |
| ACK | Anglican Church of Kenya |
| ACK | Amsterdam Compiler Kit |
| ACK | Nantucket, MA, USA (Airport Code) |
| ACK | Assistant Cook (US DoD) |
| ACK | Accounting Control Key |
| ACK | America's Career Kit (US Department of Labor) |
| ACK | Aircraftkiller (gaming) |
| ACK | Acknowledged Signal (mobile radio communication system) |
| ACK | Anti-Capitalist Kananaskis (counter G8 movement) |