Original: E.g. the C, C++, or Java standards define different Programmer Visible Macroarchitecture - although in practice the C microarchitecture for a particular computer includes UISA (Microcode Instruction Set Architecture) - a family of machines with different hardware level microarchitectures may share a common microcode architecture, and hence a UISA.
Simplified: UISA (Microcode Instruction Set Architecture): A family of machines with different hardware level microarchitectures may share a common microcode architecture, and hence called a UISA.