Hacking and computer crime
Although the word "hacking" originally refers to acts requiring great skill and knowledge of computer systems, it has by now become almost synonymous with illegal activities like breaking into protected computer systems, releasing viruses, stealing passwords or other sensitive data, denial of service and so on. Many of these activities require a certain amount of skill and knowledge and so could be seen as hacking in the traditional sense, but the motives involved are quite different.
Also, a large number of today's "hackers" do nothing more than running publicly available programs ("scripts") that automate attemtps to break into systems. While easily defeated on a one-to-one basis, the sheer number of such "script kiddies" makes them a very real threat.