When studying a foreign language, we have no choice but to resort to dictionaries time and time again to help comprehend new words and search for ways to express ourselves more effectively.
Having said that,after many years of using dictionaries as a reference, I’ve learned to not over rely on them, sometimes even going as far as doubting them. That’s because there is so much that isn’t captured in most dictionaries, especially those that translate from one language to another (i.e. Japanese->English or English->Japanese).
For example, is the word in question used by primarily men, women, or both sexes? It is used more by a certain age group? Is it more likely to be used in written or verbal language? Is it a stuffy academic word or one that is used casually as slang? Which regional dialects (方言) use the word and which do not?
In addition, information about whether a word has rude or insulting connotations is often not listed. For example, I have heard from several sources that 外人 has a negative connotation to it whereas 外国人 is more neutral, but I have never seen that stated in a Japanese to English dictionary.
It’s not that dictionaries don’t try to represent as much useful information as they can. But the fact that words are continually evolving make them a moving target that is hard to keep pace with. For example, a word that was popular a year ago may no longer be in use, and there is always new expressions cropping up. The dictionary I use the most frequently (http://dictionary.goo.ne.jp/) has a good amount of information and even has a section on newly coined phrases or words, but it’s still far from ideal.
So whats one to do? Simply asking a teacher or native speaker isn’t the magic bullet, because each person has a slightly different interpretation of words’ meanings, though it’s a good place to start. All you can do is just try to listen to the word in as many different contexts as possible. Sometimes I’ll hear a word and not quite understand how it’s meaning fits into context of the discussion, but then I’ll hear it used again later in a way that clicks in my head, after which I’ll begin to try using it in my own speech.
Manga, anime, and TV dramas are great resources for learning. But real conversation, live with a real person, provides the most rich context to learn from. Not only do you have gestures and facial expressions, but also there is typically more emotional investment. If someone in person asks you a direct question, you’re forced to listen and infer the meaning of the words they have used or else you might end up looking stupid.
Look at it a different way – do children use dictionaries when learning a first, or even second language? Very rarely. They are attentive listeners and put forth great effort into inferring meaning from new words by using all the context available to them. They might not get it the first or second time, but each time they hear a word used in context they add that data to their brain, and eventually there is enough information to fill in all the blanks.
Of course, children have a biological advantage in that their linguistic abilities and memory are typically far above an average adult. These things do gradually decline as we age, but they don’t die completely, and can be improved with training to a certain point.
I’ll give you two suggestions to help keep your linguistic juices flowing. First, try to avoid watching Japanese with English subtitles at all costs. While you’re likely to understand the story much better (and therefore enjoy it more), the part of your brain that normally struggles to think about the meaning of words takes a break. What happens is you first read the subtitle, and then hear some of the Japanese words and think “oh yeah, of course I understand the Japanese used here”. But you’ve been given a major hint to help you decode the words and grammar of the sentence. Without that hint, you’d have had to focus more on picking out individual words from a stream of syllables, thinking about their meaning in context, and figuring out what the sentence meant as a whole.
Second, don’t always jump to the dictionary to look up words whose meaning you are fuzzy on. Try to watch (or read) a bit more to see if you can guess the meaning after seeing/hearing it used a few more times. If you still don’t get it, look up the word later after some thought and you’ll have sort of a eureka moment where you say “Oh… that’s what that word meant the entire time. It makes sense now.” If you do this you’ll likely retain the meaning much better, as opposed to quickly looking up the word (without much thought about it first) and then quickly forgetting it.
On a final note, when you really have to look up a Japanese word in a dictionary, consider checking the Japanese->Japanese (国語) dictionary, as it gives much more information about words. Depending on your level this may be quite a challenge, but it in itself will help take your Japanese to the next step.