Original: Such an ASIC is often termed a SoC (system-on-a-chip). Designers of digital ASICs use a hardware description language (HDL), such as Verilog or VHDL, to describe the functionality of ASICs.
Simplified: Designers of ASIC use a hardware description language (HDL) such as Verilog or VHDL to describe the functionality of ASIC.