Michael,
Here is a link mentioned by billvanderhoof in an earlier post:
http://www.adtdl.army.mil/cgi-bin/atdl.dll/tc/9-237/toc.htm
It is an Army welding manual and it is a great resource. Some sections are very appropriate for studying for the CWI examination and there is a good definition section. I always stress the importance of definitions when studying for the CWI. Since the questions are multiple choice, sometimes the answers are very similar.
Be sure to read through the old posts in this section for some excellent advice on the CWI examination. Don’t be afraid to ask questions.
Thirdeye