I recently read this article about just how awesome the Webster's dictionary is compared to other dictionaries.. I highly recommend it.
After reading that I installed that dictionary in OSX. Then a few days later I needed to look up a Japanese word. I usually go to WWWJDIC to look things up but it's annoying to have to be online.
Then I got to thinking, Hmmm, if I was able to install a dictionary into OSX I'll bet there's a Japanese or Japanese to English dictionary. A few clicks later and BAM!, turns out there's one built in. All you have to do is turn it on.
Launch the Dictionary App. For me I was able to click the spotlight icon (🔍) in the top right and type "dictionary" then press Enter but you might have to go look in your Applications folder.
Now from the menus pick "Dictionary−>Preferences..."
Then turn on the Japanese to English dictionary and any other ones you want to use.
Now in general you can right click any word or highlight word and pick "Look Up in Dictionary".
And the definition will come up.
You can also paste a word into spotlight or of course use the Dictionary app directly.
You can also do something similar in iOS.