| Abbreviation | Definition |
|---|---|
| OJM | Osaka Journal of Mathematics |
| OKM | Opproximation of Killometers and Miles |
| OM | Order of Magnitude |
| OM | Out of Many |
| OMG | Observed Minus Gridded |
| OMMC | Online Monmouth Math Competition |
| OMSC | Ohio Mathematics and Science Coalition |
| OMSP | Olympic Mathematics and Science Partnership |
| ONCE | Odd North Central Even |
| OO | Other Orthogonal |
| OOB | Out Of Bound |
| OOC | Order Of Conditions |
| OOC | Out Of Continuity |
| OOFO | Order of Operations |
| OOSP | Object-Oriented Statistical Programming |
| OOT | Out Of Trend |
| OPLS | Orthogonal Partial Least Squares |
| OPM | Optimal Probability Measure |
| OPP | OPPosite |
| OPRA | Oriented Point Relation Algebra |