If you like the Google glossary, try Atomica instead. Once you've installed their free client, all you have to do is put your mouse pointer over any word on your screen (in any program) hold the Alt key and click. A small window will pop up giving a complete dictionary entry and links to other information about the term. There is even an audio example for pronunciation. You can also use it to check spelling in cases where no spell checker is available—link a Mudcat posting window. It includes Thesaursus entries in most cases. The dictionary used is the The American Heritage® Dictionary of the English Language, Fourth Edition. It's not the OED but it's pretty handy.

They include words like “clade” and “anagenesis” as well.

You don't have to use Atomica as a popup, you can also just open the Atomica AnswerBar with a single click and type in any word you'd like.

The Atomica client does more than just provide the definition, it also seems to evaluate the context in which the word is found. This lets it do a better job of finding the correct definition and even correctly identify terms that are more than a single word in length.

Try it, you'll like it. I'd even pay for this one if they required it.

      - Mark