Android: Looking up a word in Android is relatively easy with Google Search so well integrated. WordLookup makes it even easier by allowing you to find a dictionary definition without leaving your current app.
To look up a definition, simply select the word you want to define and use the Share menu to send it to WordLookup. You'll quickly get a toast notification (the little bubbles that appear at the bottom) with the definition of the word in question. Boom. You've saved yourself a few seconds and learned a new word. Go you.