CISC stands for "Complex Instruction Set Computer". Originally, the term was to refer to microprocessor chips that were not RISC, or "Reduced Instruction Set Computers".
As time has worn on, the difference between RISC and CISC chips has greatly diminished. In fact, most "CISC" chips now use RISC cores. Indeed, perhaps the only defining characterisitc betwen CISC and RISC chips these days is the fact that RISC chips use fixed-width instructions, while CISC chips use variable-width instructions.
CISC chips include such things as the 80x86 family.