| Abbreviation | Definition |
|---|---|
| RIRS | Rhode Island Rose Society |
| RIS | Radical Isolation Suit |
| RIS | Radiology Information System |
| RIS | Rail Interface System |
| RIS | Really Insane Search |
| RIS | Remote Install Services |
| RIS | Remote Installation Services |
| RIS | Restoratative Integral Support |
| RIS | Retail Inkjet Solutions |
| RIS | Retirement Income Specialist |
| RIS | Reverse Image Search |
| RIS | Robotics Invention System |
| RIS | Rotational Isomeric State |
| RISA | Radioactive Iodine Serum Albumin |
| RISA | Rapid Interactive Structural Analysis |
| RISA | Recording Industry of South Africa |
| RISA | Regional Integrated Sciences and Assessments |
| RISA | Regional Integrated Sciences Assessments |
| RISA | Relevant Inspiring Specific and Accurate |
| RISA | Resource Industry Suppliers Association |