| Acronym | Definition |
|---|
| SSI | Supplemental Security Income |
| SSI | Server Side Include |
| SSI | Small-Scale Integration |
| SSI | Statens Serum Institut (Denmark) |
| SSI | Strategic Studies Institute (US Army War College) |
| SSI | Scuba Schools International |
| SSI | Social Security Income |
| SSI | Statens Strålskyddsinstitut (Swedish Radiation Protection Authority) |
| SSI | Small Scale Industries |
| SSI | Single System Image (cluster of systems appearing as one system) |
| SSI | Surgical Site Infection |
| SSI | Sensitive Security Information (US DoT) |
| SSI | Solid State Imaging |
| SSI | Strategic Simulations Inc. |
| SSI | Spatial Sciences Institute |
| SSI | Survey Sampling International |
| SSI | Student Success Initiative |
| SSI | Social Security Insurance |
| SSI | Space Studies Institute |
| SSI | Server System Infrastructure |
| SSI | Soil Structure Interaction |
| SSI | Sales Satisfaction Index |
| SSI | Strålskyddsinstitutet |
| SSI | Sliding Scale Insulin |
| SSI | Sight Savers International |
| SSI | Shoulder Sleeve Insignia |
| SSI | Saint Simons Island (place name in Georgia, USA) |
| SSI | Solid State Interlocking |
| SSI | Single Sign-In (authentication) |
| SSI | Solid-State Imager |
| SSI | Size-Selective Inlet |
| SSI | Serial Synchronous Interface |
| SSI | Signal Strength Indicator |
| SSI | Soldier Support Institute |
| SSI | Silent Spring Institute |
| SSI | Spaceport Systems International |
| SSI | Ship Station Identification |
| SSI | Short-Circuited Stub Inductor |
| SSI | South-South Initiative (WHO Tropical Disease Research) |
| SSI | Scandinavian Society for Immunology |
| SSI | Sustainable Salmon Initiative |
| SSI | Software Systems Interface |
| SSI | Simpósio sobre Segurança em Informática |
| SSI | Submarine Systems, Inc. |
| SSI | Spectral Sciences, Inc. (Massachusetts) |
| SSI | Structural Significant Item |
| SSI | Satellite Software International |
| SSI | Standard Settlement Instruction |
| SSI | Secret Sensitive Information |
| SSI | Static Skeleton Interface (CORBA server-side API) |
| SSI | Specialty Skill Identifier |
| SSI | Secure Solutions International |
| SSI | Same-store Sales Index (Redbook) |
| SSI | Special Structural Inspections (aviation) |
| SSI | Shared Systems Initiative (Canada) |
| SSI | Self-Service Interface (websites) |
| SSI | Simulator Systems International |
| SSI | Site Screening Investigation |
| SSI | Systems and Synchronous, Inc |
| SSI | Spastic Society of India |
| SSI | State-Supported Institution |
| SSI | Stress-Strength Interference (reliability model) |
| SSI | Software Solutions Integrated Limited |
| SSI | Staff Sergeant Instructor |
| SSI | Sooner Scientific, Inc (Garvin, OK) |
| SSI | Screening Site Investigation |
| SSI | Standing Signal Instruction |
| SSI | Safety Significant Item |
| SSI | Scottish Society of Indianapolis (Indianapolis, IN) |
| SSI | Suspect Site Inspection |
| SSI | Single Source Integration |
| SSI | Steady-State Irradiation |
| SSI | System Standards Inc. (Philippines) |
| SSI | Single Subscriber Interface |
| SSI | Schedule Support Impact |
| SSI | Science Support Interface |
| SSI | Summit Safety, Inc (Devens, MA) |
| SSI | SIM-STIM Interface (interface for having Sims Stimulate C4ISR boxes) |
| SSI | Source Significant Information |
| SSI | Safe Sex Instructor |
| SSI | Sponsored Sales Intermediary |
| SSI | Single Source Income |
| SSI | Similar Source Integration |
| SSI | Soldier System Interface |
| SSI | Surprise Security Inspection |
| SSI | Square Spiral Inductor |
| SSI | Significant Schedule Impact |
| SSI | Sustaining Support Increment |
| SSI | Synchronous Serial Line Interface |
| SSI | Stores Station Indicator |
| SSI | Source Selection Initiative |
| SSI | Space Systems Internetting |
| SSI | Smoothing Suppression Indicator |
| SSI | Section Scan Indicator |
| SSI | Synthesis Solutions, Inc. |
| SSI | Structural Safety Inspection |
| SSI | Sub-Surface Investigation |
| SSI | Sector Scan/Scanning Indicator |
| SSI | Single-Source Investments |
| SSI | Safe Sex Initiative |
| SSI | Selective Serotonin Inhibitors |
| SSI | Single-Site Injection |