| Abbreviation | Definition |
|---|---|
| AA | Awaiting Activation |
| AAA | Authentication, Authorization, and Accountability |
| AAAA | Authentication, Authorization, Auditing, and Accounting |
| AAI | Authentication and Authorization Infrastructure |
| AAIP | Authentication and Authorization Infrastructure Project |
| AAPR | Advanced ARJ (Archived by Robert Jung) Password Recovery |
| AB | Apache Benchmark |
| ABP | AdBlock Plus |
| ABS | Active Battery Security |
| ABS | Anti Blockier System |
| ABU | Analog Back-Up |
| AC | Access Control |
| ACCE | Advanced Configurable Crypto Environment |
| ACE | Advanced Combination Encoder |
| ACE | Assured Computing Environment |
| ACES | Army Communication Encryption System |
| ACF | Access Control File |
| ACFA | Access-Control Framework Access |
| ACID | Anti-Copying In Design |
| ACIT | Advanced Countermeasures for Insider Threats |