have you try here ?
http://www.chess.com/chessopedia/
Try:
Chess Thinking: The Visual Dictionary of Chess Moves, Rules, Strategies and Concepts, by: GM Bruce Pandolfini.
It's the best chess book I've ever read for the following three reasons:
1.) the book was fun to read.
2.) it has pictures !!
3.) the information is invaluable, or priceless ... I mean ... it's worth a lot !!
I hope this helps.
Reese's Peaces
I've looked around on this site and perhaps I'm missing something, however, is there a comprehensive chess dictionary here or can anyone recommend one?