| Acronym | Meaning |
| ACIS | Advanced CCD Imaging Spectrometer |
| ACIT | Adoptive Chemoimmunotherapy |
| ACJ | Artificially Constructed Junction (in Solar Cell Fabrication) |
| ACL | Alternative Concentration Limit |
| ACL | Analytical Chemistry Laboratory |
| ACL | Average Contaminant Level |
| ACLSV | Apple Chlorotic Leaf Spot Virus |
| ACM | Aanderaa Current Meter |
| ACM | Asbestos Containing Material(s) |
| ACM | Adiabatic Channel Model |
| ACME | Aquatic Cycling Of Mercury In The Everglades |
| ACMG | American College Medical Genetics |
| ACMP | Advisory Committee On Marine Pollution (ICES) |
| ACMV | African Cassava Mosaic Virus |
| ACNFS | Advisory Committee On Nuclear Facility Safety |
| ACNK | Al2O3/(CaO + Na2O + K2O) |
| ACO | Atomic-cell Orbital |
| ACOIN | Australian Core Inventory |
| ACOP | Approved Code Of Practice (UK) |
| ACOPS | UK Advisory Committee Of Oil Pollution Of The Sea |
| ACORE | Atomic Core Orbitals |
| ACP | Air Carcinogen Policy |
| ACP | Acid Phosphatase |
| ACP | Acyl Carrier Protein |
| ACP | Alternating Current Polarography |
| ACP | Amorphous Calcium Phosphate |
| ACP | Approximate Coupled-pair (method For Correlation-energy Calcn.) |
| ACP | Automatic Correlation Partitioning |
| ACPAR | Angular Correlation Of Positron Annihilation Radiation |
| ACPCSA | Adiabatic Capture Partial Centrifugal Sudden Approximation |
| ACPD | Alternating Current Potential Drop |
| ACPF | Averaged Coupled Pair Functional |
| ACPQ | Approx. Coupled-pair (theory Cor. For Connected) Quadruply (excited Clusters) |
| ACPR | Annular Core Pulse Reactor |
| ACPTQ | Approx. Coupled Pair (theory Cor. For Connected) Triple And Quadruple Excitations |
| ACQM | Arrangement-channel Quantum Mechanics |
| ACR | Absolute Cryogenic Radiometer |
| ACR | Acute-Chronic Toxicity Ratio |
| ACR | Advanced Cracking Reactor (for Ethylene Production From Petroleum) |
| ACRE | Automatic Climatological Recording Equipment |
| ACRES | Australian Center For Remote Sensing |
| ACRIM | Active Cavity Radiometer Irradiance Monitor |
| ACRR | Annular Core Research Reactor |
| ACRS | Advisory Committee On Reactor Safeguards |
| ACRS | Applied Computational Research Society |
| ACRT | Accelerated Crucible Rotation Technique |
| ACS | American Chemical Society |
| ACS | Acute Coronary Syndrome |
| ACS | Adiabatically Corrected Sudden |
| ACSH | American Council On Science And Health |