1. To program a computer in a clever, virtuosic, and wizardly manner. Ordinary computer jockeys merely write programs; hacking is the domain of digital poets. Hacking is a subtle and arguably mystical art, equal parts wit and technical ability, that is rarely appreciated by non-hackers.
2. To break into computer systems with malicious intent. This sense of the term is the one that is most commonly heard in the media, although sense 1 is much more faithful to its original meaning. Contrary to popular misconception, this sort of hacking rarely requires cleverness or exceptional technical ability; most so-called "black hat" hackers rely on brute force techniques or exploit known weaknesses and the incompetence of system administrators.
. To jury-rig or improvise something inelegant but effective, usually as a temporary solution to a problem.