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. See hacker.
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.
3. To jury-rig or improvise something inelegant but effective, usually as a temporary solution to a problem. See noun sense 2.
n.
1. A clever or elegant technical accomplishment, especially one with a playful or prankish bent. A clever routine in a computer program, especially one which uses tools for purposes other than those for which they were intended, might be considered a hack. Students at technical universities, such as MIT, are famous for performing elaborate hacks, such as disassembling the dean's car and then reassembling it inside his house, or turning a fourteen-story building into a giant Tetris game by placing computer-controlled lighting panels in its windows.
2. A temporary, jury-rigged solution, especially in the fields of computer programming and engineering: the technical equivalent of chewing gum and duct tape. Compare to kludge.
3. A cheap, mediocre, or second-rate practitioner, especially in the fields of journalism and literature: a charlatan or incompetent.
v1. I stayed up all night hacking, and when I finally looked out the window, it was 8am.
v2. Some script kiddie hacked into the web server and trashed the database.
v3. I didn't have time to do things properly, so I just hacked together something that worked.
n1. A computerized bartender that automatically mixes your drinks and debits your account? Now THAT'S a hack.
n2. This subroutine is just a hack; I'm going to go back and put some real code in later.
n3. That two-bit pulp writer? Ah, he's nothing but a hack.
Hacked is supposed to mean unauthorized access to computers and computer networks, but not any more, now it means to post 'Hilarious' statuses on somebodies Facebook profile.
Idiot: "I totally hackedJoe's Facebook the other day!"
Normal Person: "Really, you hacked it? How?"
Idiot: "He left himself logged in and I posted a status."
Normal Person: "That's not hacking."
Being in the state of victimized by a hacker who has either installed a program into your computer or has gotten into an account of yours with programs or just goodskillz.