Hidden deep in the depths of OS X is a dictionary, not just any old dictionary but one that can be accessed at anytime. I often type a word and wonder if I’ve gotten it in the right context handily I can 'ctrl command d' and up pops a dictionary definition, alternatively you can 'right click' and select look up. You also get the option of a thesaurus or if you click ‘more’ you can even bring up a wiki page on your chosen word however if you do decide to wiki then you’ll need to have internet access.
The dictionary is the New Oxford American Dictionary, 2nd Edition and you can switch between US and UK English. By default it is set to US so us brits will have to go in and change it via preferences in the application itself. When you are in the application you can also easily increase the font size and have the definition read back to you via the in built-in text to speech service.
Interestingly the dictionary doesn’t work in MS Word 2004, probably because it has its own dictionary function.
Verdict: As a fairly unknown freebie to OS X the ability to reference a word in most applications it totally cool and it works really well.

