| Acronym | Meaning |
| MBPT | Many-body Perturbation Theory |
| MBPT(2)-GF | Second-order Many-body Perturbation Theory-green Function |
| MBPV | Mixed-basis Potential Variation (for Electronic-structure Calcn.) |
| MBR | Mobil Benzene Reduction [process] |
| MBR | Membrane Bioreactor |
| MBRS | Molecular Beam Reactive Scattering |
| MBRS | Molecular Beam Relaxation Spectrometry |
| MBRSPT | Many-body Rayleigh-Schroedinger Perturbation Theory |
| MBS | Minimum Basis Set Wave Function |
| MBSCI | Minimum Basis Set Configuration Interaction |
| MBSF | Meters Below Seafloor |
| MBSS | Molecular Beam Surface Scattering |
| MBT | Many-body Theory |
| MBT | Minimum [spark Advance For] Best Torque |
| MBTH | 3-methyl-2-benzothiazolinone Hydrazone |
| MBTS | 2-mercaptobenzothiazyl Disulfide |
| MC | Mclean-Chandler Basis Set |
| MC | Metal Carbide |
| MC CI | Multiconfigurational Configuration Interaction |
| MC CMO | Multiconfigurational Complex Molecular Orbita |
| MC-CEPA | Multiconfigurational CEPA |
| MC-DWBA | Multichannel Distorted Wave Born Approxn. |
| MC-ICPMS | Multiple-collector Inductively Coupled Plasma-mass Spectrometry |
| MC-INDO | Mol. Cluster-intermediate Neglect Of Differential Overlap |
| MC-MBPT | Multiconfiguration Many-body Perturbation Theory |
| MC-SCF | Monte Carlo Self-consistent-field |
| MC-SEA | Multichannel Static-exchange Approximation |
| MC-TD-SCF | Multiconfiguration-time Dependent-self-consistent Field |
| MCA | Manufacturing Chemist Association |
| MCA | Middle Cerebral Artery |
| MCAD | Medium Chain Acyl-CoA Dehydrogenase |
| MCAF | Monocyte Chemotactic And Activating Factor |
| MCAM | Melanoma Cell Adhesion Molecule |
| MCAO | Middle Cerebral Artery Occlusion |
| MCB | Micro-carrier Bed |
| MCC | Microcrystalline Cellulose |
| MCC | Modified Continuous Cooking [of Pulp] |
| MCC | Molecular Coupled-cluster (method) |
| MCC | Motor Control Center |
| MCCEM | Multi-chamber Concentration And Exposure Model |
| MCCHF | Multiconfiguration Coupled Hartree-Fock |
| MCCP | Mountain Cloud Chemistry Program |
| MCD | Magnetic Circular Dichroism |
| MCDF | Multi-configuration Dirac-Fock |
| MCDF-EAL | Multiconfiguration Dirac-Fock-extended Average Level (for Energy Levels And Wave Functions Calcn. For Atoms) |
| MCDF-OL | Multiconfiguration Dirac-Fock Optimum Level |
| MCDW | Matrix Continuum Distorted Wave |
| MCE | Magnetocaloric Effect |
| MCE | Microchannel Epitaxy |
| MCE | Microchip Electrophoresis |