Outpatient Department, a hospital department where patients receive diagnoses and/or treatment but do not stay overnight

Overfill Prevention Device, a safety mechanism commonly attached to the valves of propane tanks

Office of Public Diplomacy, an intra-agency organization established in the United States during the administration of Ronald Reagan

One Per Desk - an integrated personal computer and telecommunications terminal produced by ICL in the 1980s

optical path difference

o-phenylenediamine, a chemical compound

Oculopharyngeal muscular dystrophy, a muscle disease

Pico dos Dias Observatory, an astronomical observatory