central processing unit

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The part of a computer that interprets and executes instructions.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun computer hardware The part of a computer that fetches, decodes and executes instructions; attached directly to the memory. Abbreviated: CPU.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun (computer science) the part of a computer (a microprocessor chip) that does most of the data processing