(computer science) the part of a computer (a microprocessor chip) that does most of the data processing
"the CPU and the memory form the central part of a computer to which the peripherals are attached"
Initialism of central processing unit.
"The computer's CPU processes instructions and manages data flow throughout the system."
In plain English: A CPU is the main computer chip that does all the thinking and processing for your device.
"The old cpu is too slow to run my latest games smoothly."