OCN
- Discover Airlines
- ISDN User Part
- ISDN User Part
- NOCN
- National Exchange Carrier Association
- OCLC
- Oceanside Municipal Airport
- Ocwen Financial Corporation
- Oncology nursing
- Opaskwayak Cree Nation
- Open Computer Network
- Orange County Newschannel
- Original Camera Negative
- Orion Cinema Network
- Orthodox Christian Network
- Signalling System No. 7
- Three letter acronym