Open Source (Computing » General)
Open Source (Computing » Software)
**** Operating System (Academic & Science » Electronics)
**** Operating System (Governmental » Military)
**** Operating System (Computing » Drivers)
**** Operating System (Computing » Security)
** Operating System (Computing » General)
* Mouth (Medical » Physiology)
* Old School (Community » Educational)
* Ordnance Survey (Governmental » Military)
* Online Services (Computing » Networking)
* Outer Space (Governmental » NASA)
* Old Skool (Governmental » Military)
* Open System (Computing » General)
* Osmium (Academic & Science » Electronics)
* Osmium (Academic & Science » Chemistry)
* One Size (Miscellaneous » Clothes)
* Overall Survival (Medical » Oncology)
* O Sullivan (Community » Famous)
* On Service (Governmental » Military)
* On Sea (Governmental » Military)
* Off Screen (Community » Media)
* Open Server (Computing » Networking)
* Other Specifications (Governmental » Military)
* Oral Surgery (Medical » Physiology)
* Oxygen Saturation (Medical » Physiology)
Abbreviations dictionary. 2012.