A dictionary doesn't define what a community is about, and more importantly, it doesn't it redefine the purpose and type of content for which Stack Exchange was created. Stack Exchange was designed with a very specific focus in mind, somewhat different than a typical discussion forum. Sites center on a quantifiable, specific area of expertise by asking singularly answerable questions. We don't guarantee you can ask a question about anything you want on a site, and we don't create sites about "everything".
When a Lifehacks site was proposed, it wasn't exactly the dictionary definition of a subject we would likely host. If we wanted a site on this subject, we would have to narrow down the scope to what we can handle and run with it. But we wouldn't have created a site about anything in life or how to be more efficient at anything. That's just not what we do.
When you have an idea for a site, you pick the subject space,space; then you determine if Stack Exchange is the right tool for the job… and then find the best possible title to fit it. But the title you chose doesn't wholly rule the scope of the site. You wouldn't go to DIY and ask "What color should I paint my walls?", yet that is the very definition of "Home Improvement." That type of question just doesn't fit the purpose for which Stack Exchange was created.
When we pick the sites that can work on this network, we have some tough choices to make — you can either stick to subjects that only have objective answers like "will this compile?", or you can expand into much more diverse topic space, understanding the limitations of how these sites are designed to work. We chose the later.