PIR commonly stands for Passive Infrared (sensor or radiation) in electronics and security contexts, but the exact meaning can vary by field. Here are the most common definitions to clarify which one fits your context:

• Passive Infrared (sensor): A type of detector that senses infrared radiation emitted by objects (typically heat) without emitting any energy itself. Used in motion detectors and many security or lighting systems.

• Post-Consumer recycled: In plastics and packaging, PCR stands for Post-Consumer Recycled; PIR can refer to Post-Industrial Recycled materials in some contexts, though PCR is the more widely used term for recycled content from end-user products.

• Post-Industrial recycled: Also used in some supply chains to denote recycled content from manufacturing byproducts rather than consumer waste.

• Passive Infrared in cameras: For security cameras, PIR indicates the detector that triggers recording when movement is detected via infrared radiation.

If you can share the field or context (electronics, insulation, packaging, security cameras, etc.), the exact meaning will be narrowed further.