| Abbreviation | Definition |
|---|---|
| NZWA | Non-Zero Weighted Average |
| O | Obliqueness |
| O | Octant |
| O | Odd |
| O/E | Observed-to-expected ratio |
| OA | Orthogonal Array |
| OAC | Odd Auto-Correlation |
| OAE | Object Algebra Expression |
| OAL | Order in Algebra and Logic |
| OASIS | On-line Analytical and Statistical Information System |
| OAT | Opposite Angle Theorem |
| OBL | Oblong |
| OC | On Center |
| OC | Optimum Compaction |
| OCC | Odd Cross-Correlation |
| OCCAM | Opportunistic Cartesian Cosine Approximate Matcher |
| OCF | Ohtsuki, Cheung, and Fujisawa triangulation method |
| OCO | One Cancels the Other |
| OCRMs | Orthonormal Complex Rotation Matrices |
| OCSH | Optimal Canonical Separating Hyperplane |