OR
- or – (s) Oriya language (ISO 639-1 code)
- OR – (i) Operating Room (surgery) – Operational/Operations Research – (s) Oregon (postal symbol)
- ORAU – (a/i) Oak Ridge Associated Universities
- ORB – (a/i) Object Request Broker
- ORBAT – (p) Order of Battle
- ORD – (i) O'Hare International Airport in Chicago, Illinois (IATA Airport Code ORD)
- ORD – (i) Office of Research and Development – Operational Requirements Document
- ORF – (i) Operational Readiness Float
- ori – (s) Oriya language (ISO 639-2 code)
- ORISE – (a) Oak Ridge Institute for Science and Education
- orm – (s) Oromo language (ISO 639-2 code)
- ORNL – (i) Oak Ridge National Laboratory
- ORR – (i) Oak Ridge Reservation (U.S. DOE) – Office of Rail Regulation (UK government) – Office of Refugee Resettlement – (CIA) Office of Research and Reports – Operational Readiness Rate – Operational Readiness Review
- ORSA – Oxacillin-resistant Staphylococcus aureus – Operations Research Society of America
Read more about this topic: List Of Acronyms And Initialisms: O