| Institutional Research Office | Academic & Science |
| Investor Relations Officer | Business |
| International Relations Officer | Business |
| Inter-Religious Organization | Community |
| In Respect Of .... | Community |
| Include Route Object | Computing |
| Intelligence Recon Operative | Computing |
| Internaltional Ragnarok Online | General |
| Iron Rock Offroad | General |
| Impact Resistant Outerwrap | General |
| Independent Rental Owners | General |
| Independent Review Organizations | General |
| Itial Responding Officer | General |
| International Relations Office | General |
| Independent Review Office | General |
| International Robot Olympiad | General |
| Independent Reviewing Officer | General |
| In Receipt Of | General |
| Internationale Rettungshunde Organisation | General |
| Information Resource Officer | General |
| In Region Of | General |
| Independnat Reviewing Officer | General |
| Internal Review Office | Governmental |
| Independent Review Organization | Governmental |
| International Relief Organization | Governmental |
| Institution of Railway Operators | Governmental |
| Institute for Research in Ophtalmology | Governmental |
| International Refugee Organization (WWII) | Governmental |
| International Relations Officers | International |
| International Raspberry Organization | International |
| International Refugee Organization | International |
| International Ragnarok Online | Internet |
| Internal Redirection/Overlay | Internet |
| Intended Rehabilitation Objective | Medical |
| Iroquoian languages | Regional |
| International Race Officer | Sports |
