| Acronym | Definition |
|---|
| UIN | User Identification Number |
| UIN | Unique Identifying Number |
| UIN | User Inactivity Monitor |
| UIN | Universal Identification Number |
| UIN | Universal Internet Number (ICQ) |
| UIN | Unique Identification Number |
| UIN | University Identification Number |
| UIN | User Identification Number (ICQ) |
| UIN | Quincy, IL, USA - Baldwin Field (Airport Code) |
| UIN | University Information Network (Egypt) |
| UIN | Unit Identification Number |
| UIN | Urban Investment Network (Urban Land Institute) |
| UIN | Union Inspection Notice |
| UIN | Unité d'Imagerie Numérique (French: Digital Imaging Unit; radiology) |
| UIN | Useless Inert Nothing |
| UIN | Unemployment Identification Number |
| UIN | Union Improvement Notice (UK) |