Minimal computing is, broadly, a set of practices and approaches to computing that tends toward simplicity, reducing barriers to access and engagement with digital tools, resources, and methodologies.
The Minimal Computing Working group offers a wonderful and succinct definition on their website:
"We use 'minimal computing' to refer to computing done under some set of significant constraints of hardware, software, education, network capacity, power, or other factors. Minimal computing includes both the maintenance, refurbishing, and use of machines to do DH work out of necessity along with the use of new streamlined computing hardware like the Raspberry Pi or the Arduino micro controller to do DH work by choice. This dichotomy of choice vs. necessity focuses attention on computing that is decidedly not high-performance. By operating at this intersection between choice and necessity minimal computing forces important concepts and practices within the DH community to the fore. In this way minimal computing is also an critical movement, akin to environmentalism, asking for balance between gains and costs in related areas that include social justice issues and de-manufacturing and reuse, not to mention re-thinking high-income assumptions about 'e-waste' and what people do with it. Minimal computing thus relates to issues of aesthetics, culture, environment, global relationships of power and knowledge production, and other economic, infrastructural and material conditions."