| Acronym | Definition |
|---|
| PEI | Prince Edward Island (Canada) |
| PEI | Petroleum Equipment Institute (Tulsa, OK, USA) |
| PEI | Proyecto Educativo Institucional (Spanish: Institutional Education Project; Colombia) |
| PEI | Polyethylenimine |
| PEI | Porcelain Enamel Institute |
| PEI | Percutaneous Ethanol Injection |
| PEI | Polyether Imide (thermoplastic) |
| PEI | Paul-Ehrlich Institute (Germany) |
| PEI | Photo Electronic Imaging (magazine) |
| PEI | Professional Education Institute |
| PEI | Professional Engineers in Industry (division of NSPE) |
| PEI | Plant Equipment, Inc. |
| PEI | Photofabrication Engineering, Inc (Milford, MA) |
| PEI | Pereira, Colombia - Matecana (Airport Code) |
| PEI | Principal End Item |
| PEI | Physical External Interface |
| PEI | Proyecto Educativo Integral (Spanish; Guatemala) |
| PEI | Pulmonary Interstitial Emphysema |
| PEI | Primary Energy Intensity |
| PEI | Photoelectric Injector |
| PEI | Performance Effectiveness Index |
| PEI | Profile for Enterprise Integration |
| PEI | Preliminary Equipment Index |
| PEI | Positive Enemy Indication |
| PEI | Professional Engineering Institution (UK) |
| PEI | Plan Estrategico Institucional (Spanish: Institutional Strategic Plan; Peru) |
| PEI | Perry Ellis International (Miami, FL) |
| PEI | Private Equity Intelligence (now Preqin) |
| PEI | PoeticExperiences, Inc. |
| PEI | Prevention and Early Intervention (various locations) |
| PEI | Pacific Ethanol, Inc. (Sacramento, CA) |
| PEI | Private Educational Institution (classification) |
| PEI | Patient Education Institute (healthcare software) |
| PEI | Pack Expo International (Packaging Machinery Manufacturers Institute) |
| PEI | Playboy Enterprises International (Chicago, IL) |
| PEI | Private Equity International (various locations) |
| PEI | Physical Education Index (resource; Cambridge Scientific Abstracts) |