As a returning therapist who's been out of the field for a while, I wholeheartedly recommend this book. As the title implies, it is a DICTIONARY, and as such, defines terms. (I say this because the other reviewers were obviously looking for a different type of book, such as the equally excellent, Quick Reference to Occupational Therapy by Reed. When I was fresh out of OT school, I found that book very handy, and its appendices are great, too.) However, since I now need a dictionary tailored for OTs, this book is perfect for my purposes. And the appendices are extremely helpful.
So, if you took a long break from OT, are changing practice areas, or have noticed that terminology has changed since you graduated school, get this book. It will make reading charts and deciphering jargon at the clinic much easier. You might also want to get the Quick Reference to Occupational Therapy book by Reed, but note that it doesn't provide definitions, as it is not a dictionary.