| Acronym | Meaning |
| PS1 | Presenilin 1 |
| PSA | Potentiometric Stripping Analysis |
| PSA | Pressure Sensitive Adhesive |
| PSA | Pressure Swing Adsorption (gaseous Waste Treatment) |
| PSA | Prostate-specific Antigen |
| PSA-CCSD | Partially Spin Adapted-CCSD |
| PSB | Product Safety Branch |
| PSB | Photosynthetic Bacteria |
| PSC | Polar Stratospheric Clouds (in Antarctic) |
| PSC | Primary Sclerosing Cholangitis |
| PSCA | Periodic Small-cluster Approach (a Many-body Technique In Electronic-structure Calcns.) |
| PSCC | Pseudostate Close Coupling |
| PSCE | Partially Spin Coupled Echo |
| PSCF | Potential Source Contribution Function |
| PSCI | Partitioned (orbital Hessian) Super-configuration Interaction |
| PSCI | Pseudo Configuration Interaction |
| PSD | Passive Sampling Device(s) (for Air Pollution) |
| PSD | Photon Stimulated Desorption |
| PSD | Particle Size Distribution |
| PSD | Pore Size Distribution |
| PSD | Position Sensitive Detector |
| PSD | Post-source Decay |
| PSD | Postsynaptic Density |
| PSD | Prevention Of Significant Deterioration |
| PSD | Pulse Shape Discrimination |
| PSDF | Power Systems Development Facility |
| PSEM | Point Source Exposure Model |
| PSEP | Polyhedral Skeletal Electron Pair (for Metal Clusters) |
| PSES | Pretreatment Standards For Existing Sources |
| PSF | Point Spread Function |
| PSFT | Progressive Saturation Fourier Transform |
| PSG | Phosphosilicate Glass |
| PSHF | Pseudospectral Hartree-Fock |
| PSI | Pollution Standard Index |
| PSI | Pounds Per Square Inch |
| PSI-BLAST | Position-specific Iterated BLAST |
| PSID | Photon Stimulated Ion Desorption |
| PSII | Photosystem II |
| PSII | Plasma Source Ion Implantation |
| PSIM | Phase Shifting Interferential Microscopy |
| PSIT | Plasma Source Ion Trap |
| PSL | Photostimulated Luminescence |
| PSL | Polystyrene Latex |
| PSLC | Polymer-stabilized Liquid Crystal |
| PSM | Process Safety Management |
| PSM | Pflanzenschutzmittel; Pesticides |
| PSMA | Prostate Specific Membrane Antigen |
| PSMBE | Plasma Source Molecular Beam Epitaxy |
| PSMO | Pseudo MO |
| PSMS | Plasma Source Mass Spectrometry |