| Abbreviation | Definition |
|---|---|
| ORLS | Oconee Regional Library System |
| ORMS | On-line Research and Media Skills |
| OSBL | Open Source Business Library |
| OSDL | Oregon Spatial Data Library |
| OSL | Ocean State Libraries |
| OSL | OHBA Software Library |
| OSL | Oregon State Library |
| OSLIS | Oregon School Library Information System |
| OSLO | Open Source Library for OCL |
| OTL | Ontonagon Township Library |
| OTLA | Ohio Theological Library Association |
| OTR | Oral Tradition Room |
| OTSS | Oxford Text Searching System |
| OVAL | Ohio Valley Area Libraries |
| OVB | Ohio Valley Branch |
| OVD | OverDue |
| OWF | Objectionable Words Filter |
| OWL | Online With Libraries |
| OWLS | Outagamie Waupaca Library System |
| p.p. | past participle |