| Acronym | Definition |
|---|
| IIR | Infinite Impulse Response (digital filter design and signal processing) |
| IIR | Institute for International Research |
| IIR | Institute of Innovation Research (Japan) |
| IIR | International Institute of Refrigeration (est. 1908) |
| IIR | Infrared Imaging Radiometer |
| IIR | Incremental Image Rendering |
| IIR | Infinite Impulse Response |
| IIR | Inter Interface Relationships |
| IIR | Institute for Intergovernmental Research |
| IIR | Institute of International Relations |
| IIR | Industry Issue Resolution (pilot program of US Internal Revenue Service and Treasury Department) |
| IIR | Imaging Infrared |
| IIR | Installment to Income Ratio (finance) |
| IIR | Industrial Information Resources |
| IIR | International Institute of Reflexology |
| IIR | Intelligence Information Report |
| IIR | Intelligent Information Retrieval |
| IIR | If I Recall |
| IIR | Interactive Information Retrieval |
| IIR | Indo-Iranian (linguistics) |
| IIR | Immediate Impulse Response |
| IIR | Halogenated Butyl Rubber |
| IIR | Injury Incidence Rate |
| IIR | Imagery Interpretation Report |
| IIR | Intermediate-Node Initiated Reservation |
| IIR | Interlinking Internal Reference |
| IIR | Inter-Interface Relationships |
| IIR | Imagery Intelligence Report |
| IIR | Inertial Instrument Unit |
| IIR | Initial Imagery Report |
| IIR | Isstituto Italiano del Rame |
| IIR | Intermediate Information Requirement |