ASIC is an abbreviation, standing for ‘Application Specific Integrated Circuit’.
An integrated circuit is a microchip – a set of circuits which are manufactured together as a single component, on top of a small plate made from semiconductor material such as silicon. This stands in distinction to a ‘discrete circuit’ which is put together using multiple components which were manufactured separately.
An application specific integrated circuit is therefore a microchip which has been designed to perform a specific job, in distinction to the kind of general purpose microchip which you would expect to find inside most computers.
Within the context of this blog the term ‘ASIC’ most likely refers to a microchip which has been designed specifically for performing the Proof of Work calculations used for the mining of cryptocurrencies like Bitcoin.
Various different cryptocurrencies operate using different mining algorithms. Bitcoin, for example, uses the SHA-256 algorithm. A Bitcoin ASIC is therefore a microchip which has been designed solely for performing SHA-256 calculations as quickly and efficiently as possible. Cryptocurrencies with different mining algorithms would need an ASIC designed specifically for the kind of calculations performed as part of that algorithm.