A term broadly used to describe hardware and software research and development, and modification. "To hack" essentially means "to plow," and refers to assembling and modifying computer systems and programs. Programmers with high technical capabilities are given the honorary title of hacker.
The word can also refer to invading another person's computer, but the correct term is "cracking." Programmers who are adept at cracking refer to themselves as hackers. As a result, hacking is often taken to mean a criminal act.
Person 1 : Hi, I'm a hacker!
Person 2 : OMG WTF U STEAL PPLS BANK ACCOUNTZZ???
Person 1 : No you moron, that would be a cracker.