Math Science Institute, a major in Brooklyn Technical High School
Media Sports Investment, the international fund of investors that runs Sport Club Corinthians Paulista
Medium Scale Integration, a kind of electronic chips
Message Signaled Interrupts, a PCI 2.2 interrupt mechanism
Metal-Support Interaction, a phenomenon in catalysis whereby unique (electronic) properties are created at the interface of a metal and the material on which it dispersed on leading to the creation of sites with the potential for catalytic behaviour
Microsoft Installer, an installer system written by Microsoft for Windows platforms
Micro-Star International, a computer component manufacturer
Mindless Self Indulgence, an American punk band
Mobile Systems International
Movie Star, Inc. (AMEX:MSI), a publicly-traded clothing manufacturer
Movimento sociale italiano, an Italian neo-Fascist political party
Museum of Science and Industry in Chicago
Multi-Simulation Interface, a method for interconnecting simulators