A newly coined word is more likely not to be understood by your readers. Consider: your readers might not hang out in the particular circle where the word was coined and is known. In effect, such a word is not different from a dialect word that's only likely to be understood in a specific city or state. There are even words that would only be understood in, say, Australia, but no-where else in the English-speaking world.
Since it is quite likely that your readers would not understand the word, you need to help them understand. In non-fiction writing, you can provide an explanation or a definition. Where you need more organic usage, such as in fiction writing, you should use the word in such a way that it's meaning is self-evident, similar to how writers sometimes use invented words.
You need to consider who your audience is: if you're writing for a small circle of people who are likely to be already familiar with the word, you need to provide less explanation than if you're writing for a larger market that might include non-native speakers who would rely on a dictionary to help with unfamiliar words, and as you state, would find nothing there. Similarly, writing for a highbrow publication, words that are "too new" and "slang" would be considered inappropriate.
Also, in fiction writing, consider who would be using such words. A 19th-century heroine, or a modern elderly gentleman are not likely to use words recently coined by an internet community.