Is it possible to bind my Mac OSX Dictionary.app to Google Translate?
Unfortunately it doesn't appear to be possible, or at least straightforward. As an alternative, you may want to consider creating an OS X Service that opens Google Translate in a browser window, for any highlighted word or phrase you have selected.

If this sounds suitable, follow the procedure below:

Creating a translation Service


Open the Automator app from your Applications folder
Select Service as the type of document and click Choose
In the window that appears, click the search field and type 'AppleScript'
Drag and drop the Run AppleScript action from the list on the left into the area labelled 'Drag actions or files here to build your workflow'


Copy the script below and paste it into the Run Applescript action:

on run {input, parameters}
    set phrase to input as string
    set phrase to quoted form of phrase

    set ui_lang to "en"
    set from_lang to "en"
    set to_lang to "zh-CN"

    do shell script "open 'https://translate.google.com/?hl='" &amp; ui_lang &amp; "'&amp;sl='" &amp; from_lang &amp; "'&amp;tl='" &amp; to_lang &amp; "'&amp;text='" &amp; phrase
end run


Your window should look like the following:



There are three values that you may want to change in the above script:


ui_lang - the language used for the page interface
from_lang - the source language
to_lang - the destination language


Change one or more of these to achieve the desired translation. To find the correct language parameters, refer to the Language Reference. In the example above en refers to English, and zh-CN to Chinese (Simplified).

After making your changes, click File > Save... and in the panel that appears type a suitable name (e.g. Translate English to Chinese).



Using the translation Service

After saving your workflow above, you can make use of your translation service with one of the following two methods: 

1. The Service Menu method


Highlight a word or phrase in any application
Click the Application Menu to the right of the Apple icon (), then click Services and Translate English to Chinese (or the name you gave your Service when saving it):




2. The Contextual Menu method


Highlight a word or phrase in any application
Right-click the text and select Services then Translate English to Chinese (or your custom named Service):






Whichever method you use, a browser window should appear with your translated text: