Dictionary.com, along with its affiliate Thesaurus.com, is one of the leading online word-reference sites. And the Dictionary.com app is just as good.
When you open the app, you see a very simple screen, and the program is in dictionary mode. The most prominent item is the search bar. Simply type the word you want to look up and press Search; up pops the definition in all of its forms. The app shows the phonetic pronunciation, of course, but if you tap the speaker icon it will say the word out loud, too. That's a killer feature.
Four icons live at the top of the screen: Dictionary is the first, followed by Thesaurus.com, History, and Word of the Day. Press Thesaurus, and the app produces synonyms for the word you just looked up (or you can enter a new one in the search bar). The History pane is simply a list of all the words you have looked up, so it's easy to go back and see any of them again. You can also delete words from the list to cut down clutter.
Word of the Day is a fun little feature. As you might imagine, it suggests a new word every day and gives you the definition. Neat. But it also goes a step further and allows you to choose a Spanish word of the day, which is really cool if you're working on your Español. The app comes with a widget, too; it's a 4x1 affair that you can put on your home screen so that you don't even have to open the app to get your Word of the Day fix.
The Dictionary.com app doesn't really have a weakness. You need an active data connection to use it, but other than that, it's rock-solid.