| Physical Science Informatics | Academic & Science |
| Paranormal Studies Institute | Academic & Science |
| Post Secondary Institution | Academic & Science |
| Published Subject Indicator | Academic & Science |
| Paint Storm Indoor | Academic & Science |
| Psychology Student Instructor | Academic & Science |
| Parapsychology Studies Institute | Academic & Science |
| Pacific Sulfur Investigation | Academic & Science |
| Pacific Stratus Investigation | Academic & Science |
| Perimeter Scholars International | Academic & Science |
| Planetary Science Institute | Academic & Science |
| Probability, Statistics, and Inference | Academic & Science |
| Personalized System of Instruction | Academic & Science |
| Psychology Slander Intuition | Academic & Science |
| Pasni | Airport Code |
| Patient Services Inc | Business |
| Pre-shipment Inspection (Technical) | Business |
| Physical Sciences Inc | Business |
| Professional Service Incorporated | Business |
| Patient Services Incorporated | Business |
| Power Solutions International | Business |
| Psychological Society of Ireland (Cumann Siceolaithe Eireann) | Business |
| Publisher Services Incorporated | Business |
| Polymer Systems Incorporated | Business |
| Praeger Security International | Business |
| Performance Systems International | Business |
| Professional Service Industries | Business |
| Porta Systems Corporation | Business |
| Pharmaceutical Society of Ireland | Business |
| Pason Systems, Incorporated | Business |
| Printers & Stationers, Inc. | Business |
| Pet Sitters International | Business |
| Products, Services, and Ideas | Business |
| Pressure Systems Incorporated | Business |
| Pure Style Incorporated | Business |
| Pusat Sumber Ilmu | Business |
| Paleontology Studies Incorporation | Business |
| Provider of Statistical Information | Business |
| Publisher Services Inc | Business |
| Personnel Staffing Inc | Business |
| Production Services International | Business |
| Pounds Per Square Inch | Chemistry |
| Perfect Salvation Initiation | Community |
| Paul Scherrer Institute | Community |
| Poetry Slam Incorporated | Community |
| Psychological Society of Ireland | Community |
| Published Subject Identifier | Community |
| Philanthropic Service for Institutions | Community |
| Please Stay Indoors | Community |
| People Synergistically Involved | Community |
| Postponing Sexual Involvement | Community |
| Postpartum Support International | Community |
| Packet Switching Interface | Computing |
| Performance Schema Instrumentation | Computing |
| Processing Speed Index | Computing |
| Personal Software Inspector | Computing |
| Packetnet Systems Interface | Computing |
| Pitch Synchronous Innovation | Computing |
| Post Script Interpreter | Computing |
| Packet Switched Interface | Computing |
| Peripheral System Interconnect | Computing |
| Poly Silicon | Computing |
| Prime System Integrator | Computing |
| Product Support Integrator | Computing |
| Performance System Integrator | Computing |
| Portable Site Information | Computing |
| Page Speed Insights | Computing |
| Privacy Secure Inc. | Computing |
| Personal Security Inspector | Computing |
| Performance Summary Interval | Computing |
| Process to Support Interoperability | Computing |
| Programmable Serial Interface | Computing |
| Precise Stylus Input | Computing |
| Passive Income | Cryptocurrency |
| Nexus Protocol | Cryptocurrency |
| Packaging Services Industries | General |
| People Seeking Intelligence | General |
| Pki Secure Interface | General |
| Potentially Shippable Increment | General |
| Performance Silvias And Imports | General |
| Pride Service and Integrity | General |
| Paranormal and Supernatural Investigation | General |
| Pre shipment Inspection | General |
| Pound Square Inch | General |
| Prospect Success Indicator | General |
| Passion Success Innovation | General |
| Peripheral Sensor Interface | General |
| Periodic Smoke Inspection | General |
| Pole Side Impact | General |
| Price Satisfaction Index | General |
| Pressure Safety Information | General |
| Parking Solutions Inc. | General |
| Pressure Stuck Inside | General |
| Process and Systems Integration | General |
| Performance Studies international | General |
| Public Services International | General |
| Population Services International | General |
| Persistence Service Interface | General |
| Purchase Sales Inventory | General |
| Purchase Sales and Inventory | General |
| Proteomics Standards Initiative | General |
| Photon Systems Instruments | General |
| Pollutant Standards Index | General |
| Plasma Surface Interactions | General |
| Polymorphic Spreadsheet Interpreter | General |
| Phillips Service Industries | General |
| Pneumonia Severity Index | General |
| Pollution Standards Index | Governmental |
| Personal Security Investigation | Governmental |
| Personal Success Institute | Governmental |
| Potential Security Informant | Governmental |
| Palestine Standards Institution | Governmental |
| Pre-Sentence Investigation | Governmental |
| Present Serviceability Index | Governmental |
| Private Sector Involvement | Governmental |
| Post Shipment Inspection | Governmental |
| Pollution Standard Index | Governmental |
| Pharmaceutical Security Institute | Governmental |
| Public Subject Identifier | Governmental |
| Product Stewardship Institute | Governmental |
| Police Sub Inspector | Indian Police Rank |
| Principles for Sustainable Insurance | Insurance |
| Planned Systems International | International |
| Para Su Información | International |
| Partai Sosialis Indonesia | International |
| Performance Solutions International | International |
| Partido Socialista Interior | International |
| Peer Search Infrastructure | Jobs |
| Position Specific Iterated | Maths |
| Pound per Square Inch | Measurement Unit |
| Pseudo-Stereo Imaging | Medical |
| Parenting Stress Index | Medical |
| Pre-Sensory Intuition | Medical |
| Pharmacy Service Initiative | Medical |
| Passive Sonic Irrigation | Medical |
| Pleural Space Infection | Medical |
| Protein Structure Initiative | Medical |
| Prostaglandin Synthetase Inhibitor | Medical |
| Pain, Spasm, and Inflammation | Medical |
| Psychiatric Solutions Incorporated | Medical |
| Proliferation Security Initiative | Military and Defence |
| Personnel Security Investigation | Military and Defence |
| Proliferation Security Initiative Psi Pounds Per Square Inch | Military and Defence |
| Packetnet System Interface | Networking |
| Pasni, Pakistan | Regional |
| Presidential's Special Initiatives | Regional |
| Program Structure Interface | Softwares |
| Program Specific Information | Softwares |
| Pounds Per Square Inch (lb/in2 Preferred) | Space Science |
| Power Static Inverter | Space Science |
