| ACT | Alternative Control Technique | - | Computer Acronyms(common) |
| ACT | Acoustic Charge Transport | - | Computer Acronyms(common) |
| ACT | Activated Clotting Time | - | Computer Acronyms(common) |
| ACT | Activated Complex Theory | - | Computer Acronyms(common) |
| ACT | R -ACT-Rational (cognitive Model) | - | Astronomy |
| ACT | R/PM -ACT-R/Perceptual-Motor (cognitive Model) | - | Astronomy |
| ACT | Adaptive Control Of Thought (cognitive Model) ? Australian Capital Territory (postal Symbol) ? American College Test(ing Program) | - | Astronomy |
| ACT | Atmospheric Chemical Transformations | - | Business and Finance |
| ACT | accounting control transaction
| - | Human Genome |
