Language is given meaning by context. We've all heard that before, it was a drilled and repeated point in high school english, college writing, and every linguist will have an opinion about it. You will likely understand the people who you spend the most time with. Another aspect of this is situational. If it's your birthday, and someone says, "Haps," to you, it means the same thing as if someone said, "Happy Birthday" to you. But if it's three months after your birthday and you fell into the water at duck pond because you tripped over a tree root, and someone says, "Haps," to you, it most certainly won't mean happy birthday. This is why it's important to write to your audience. Obviously, if you're writing a book, you need to understand the individuals you want to reach. The same goes for other publications. Blogging, advertising, newspaper articles; if you're writing to baristas, use their lingo. To talk about horses to a rancher, don't call then all ponies (unless he breeds ponies, then call away).
Use words your audience will understand—but in order to do that, you have to know you audience beyond just 'intended target audience.' You have to meet people who read those books, who watch those movies. You have to go to coffee shops and talk to baristas; and cattle ranches and meet people who work with horses, who understand them and breed them and who can tell you all about them.
If you can communicate with your audience on their level, your work will actually mean something to them. And, after all, creating something that has meaning is what we're all aiming for.