A tool or technique that makes some aspect of one's life easier or more efficient. Also: life hack.
lifehacker, life hackern.
lifehacking, life hackingpp.
O'Brien summed up his research in a speech called "Life Hacks," which he delivered in February 2004 at the O'Reilly Emerging Technology Conference. Five hundred conference-goers tried to cram into his session, desperate for tips on managing info chaos. When O'Brien repeated the talk the next year, it was mobbed again. By the summer of 2005, the "life hacks" meme had turned into a full-fledged grass-roots movement. Dozens of "life hacking" Web sites now exist, where followers of the movement trade suggestions on how to reduce chaos. The ideas are often quite clever: O'Brien wrote for himself a program that, whenever he's surfing the Web, pops up a message every 10 minutes demanding to know whether he's procrastinating. It turns out that a certain amount of life-hacking is simply cultivating a monklike ability to say no.
Clive Thompson, "Meet the Life Hackers," The New York Times, October 16, 2005
The term "lifehack" is derived (if a term still in its infancy needs derivation) from the technical hacks that programmers and other geeks have set up for themselves to make their lives easier. This usually means methods of organizing data, little utilities to synchronize files, one-off scripts that automate daily tasks, etc. These things are all personal, often suited entirely to the situation and not shared with anyone. The term surfaced when there was a suggestion to share these and see if others could benefit from these "life hacks."
The term, being more generic than the original derivation, was expanded to a broader definition as the meme spread. Today, lifehacks are basically anything that is a solution to an everyday problem, frustration, etc. As a result, we’re seeing the term used to describe solutions to getting organized, losing weight, public speaking, doing your professional job better, time management, etc. As such, the current useage probably more accurately reflects the term itself.
J Wynia, "What is a Lifehack or Lifehacking?," The Glass is Too Big, December 5, 2005
Danny O'Brien, "Life Hacks: Tech Secrets of Overprolific Alpha Geeks," Emerging Technology Conference, February 11, 2004