| Abbreviation | Definition |
|---|---|
| INVOL | Involuntary |
| IO | Incoming Order |
| IO | Information Objectives |
| IO | Information Operation |
| IO | Intelligence Officer |
| IO | Intelligence Oversight |
| IO | Intermediate Objective |
| IO | International Officer |
| IOA | Independent Operational Assessment |
| IOBC | Infantry Officer Basic Course |
| IOC | Indoor Obstacle Course |
| IOC | Industrial Operations Command |
| IOC | Infantry Officer Course |
| IOC | Initial Operational Capability |
| IOC | Intelligence Operations Center |
| IOC | International Olympic Committee |
| IOC | Investigations Operations Center |
| IOCD | Initial Operational Capability Date |
| IOCF | Information Operations Career Field |
| IOD | Input/ Output Device |