| Acronym | Meaning |
| SMM | Spin Matrix Mapping |
| SMMO | Strictly Monomer Molecular Orbital |
| SMMR | Scanning Multichannel Microwave Radiometer |
| SMO | Sample Management Office (US EPA) |
| SMO | Statistical Model Of Overlap |
| SMOC | Standard Mean Ocean Chloride |
| SMOGSTOP | Statistical Model Of Ground-level Short Term Ozone Pollution |
| SMOKE | Surface Magneto-optic Kerr Effect |
| SMOW | Standard Mean Ocean Water |
| SMP | Soluble Microbial Products |
| SMP | Submitochondrial Particle |
| SMPR | Specific Methane Production Rate |
| SMR | Standardized Mortality Ratios |
| SMRI | Swedish Meat Research Institute |
| SMS | Single Molecule Spectroscopy |
| SMSA | Soft-core Mean Spherical Approxn. |
| SMSI | Strong Metal-support Interaction |
| SMSO | Spinor Molecular Symmetry Orbital |
| SMSX(ALPHA) | Overlapping-sphere Multiple-scattering X(alpha) |
| SMT | Standards |
| SMT | Surface Mount Technology |
| SNAP | Soluble NSF Attachment Protein |
| SNAP | System For Nuclear Auxiliary Power |
| SNAP | Significant New Alternative Policy |
| SNARE | Soluble NSF Attachment Protein Receptor |
| SNARL | Suggested No-adverse Response Level |
| SNCR | Selective Noncatalytic Reduction |
| SNDA | Supplemental New Drug Application |
| SNF | Spent Nuclear Fuel |
| SNFC | Sulfonated Naphthalene-formaldehyde Condensates |
| SNG | Synthetic Natural Gas |
| SNICS | Source Of Negative Ions By Cesium Sputtering |
| SNIF | Site-specific Natural Isotope Fractionation |
| SNIFTIRS | Subtractively Normalized Interfacial Fourier Transform IR Spectroscopy |
| SNL | Sandia National Laboratory |
| SNMS | Secondary Neutral Mass Spectrometry |
| SNMS | Sputtered Neutral Mass Spectrometry |
| SNO | Sudbury Neutrino Observatory |
| SNO | Spin Natural Orbital |
| SNOM | Scanning Near-field Optical Microscopy |
| SNP | Single-nucleotide Polymorphism |
| SNP | Sodium Nitroprusside |
| SNPS | Space Nuclear Power System |
| SNR | Signal-to-noise Ratio |
| SNR | Supernova Remnant |
| SNRNP | Small Nuclear Ribonucleoprotein |
| SNS | Spallation Neutron Source |
| SNS | Separation Network Synthesis (chemical Engineering Design) |
| SNS | Sympathetic Nervous System |
| SNUR | Significant New Use Rule |