| Acronym | Definition |
|---|
| OP | Opinion |
| OP | Operator (IRC) |
| OP | Opus (Latin: A Work; used in referring to music) |
| OP | Original Poster |
| OP | Operation/Operational |
| OP | Opportunity (Ads) |
| OP | Output (Hyper Logo command) |
| OP | Opera |
| OP | Output |
| OP | Opposite (volleyball position) |
| OP | Optical |
| OP | Other People |
| OP | One Piece (Anime) |
| OP | Osteoporosis |
| OP | Outpost (gaming) |
| OP | Outpatient |
| OP | Office of the President |
| OP | Out of Print |
| OP | Oak Park (Illinois) |
| OP | Overland Park (Kansas) |
| OP | Office Professional |
| OP | Original Poster (internet newsgroups and message boards) |
| OP | Ocean Pacific |
| OP | Operating Procedure(s) |
| OP | Oral Presentation |
| OP | Overpowered (gaming) |
| OP | Order Processing |
| OP | Operating Profit |
| OP | Off-Peak (time) |
| OP | Output Power |
| OP | Outreach Program |
| OP | Optimus Prime (Leader of the Autobots, icon of the 80s) |
| OP | Order of Preachers (Roman Catholicism; Dominican) |
| OP | Opposing Party (legal notation and billing) |
| OP | Organized Play (gaming) |
| OP | Order of Precedence |
| OP | Organophosphate (insecticide) |
| OP | Office of Policy (Social Security) |
| OP | One Power (Wheel of Time series) |
| OP | Operator Panel |
| OP | Office Productivity (course) |
| OP | Operationssaal (German: Operating Room) |
| OP | Observation Post |
| OP | Optical Power |
| OP | Old Patient |
| OP | Olympic Peninsula (Washington) |
| OP | Organophosphorus (pesticide) |
| OP | Operating Plan |
| OP | Original Production |
| OP | Open Pollinated (botany) |
| OP | Opening Post (internet message boards) |
| OP | Opportunities Page (CECOM) |
| OP | Operating Pressure |
| OP | Old Persian (linguistics) |
| OP | Ordo Praedicatorum (Latin: Order of Preachers; formal name of Dominicans, a Catholic religious institution) |
| OP | Observation Point |
| OP | Over Powered (gaming) |
| OP | Outpatient Pharmacy |
| OP | Oil Purifier |
| OP | Operations Order |
| OP | Oxidative Phosphorylation |
| OP | Order Point |
| OP | Osmotic Pressure |
| OP | Orthographic Projection |
| OP | Operations Procedures |
| OP | Ordinis Praedicatorum (Latin: Order of Preachers) |
| OP | Order of the Pelican (Society for Creative Anachronism) |
| OP | Operation Point |
| OP | Other Procurement |
| OP | Operation Officer (Navy) |
| OP | Optional Procedure |
| OP | Offensive Power (online gaming) |
| OP | Operational Picture |
| OP | Oxygen Pressure |
| OP | Occupation Permit (Hong Kong) |
| OP | Occiput Posterior (fetal position) |
| OP | Osteitis Pubis |
| OP | Over-Proof (of alcohol) |
| OP | Operation Register |
| OP | Oral Production (test) |
| OP | Opacity Project |
| OP | Original Pack (pharmacology) |
| OP | Operations Panel |
| OP | Optimal Partitioning (sectorization method) |
| OP | Oral Participation |
| OP | Opponens Pollicis |
| OP | Oil Pulling |
| OP | Oligodendrocyte Progenitor |
| OP | Originating Party |
| OP | Operator Personal |
| OP | Orbiter Payload |
| OP | Olden Polynice (basketball player) |
| OP | Orbit Prediction |
| OP | Ordnance Pamphlet |
| OP | Ohjelmointiputka (Finnish programming site) |
| OP | Ordnance Publication |
| OP | Operational Phase/Project |
| OP | Overnight Per Diem |
| OP | Dominican Sisters of Divine Providence (religious order) |
| OP | Opponents Pollicis |
| OP | Overlap Pulsing |