Comprehensive dictionaries of economic terms can be viewed from a number of online sources, including The Economist and the Dictionary of Economics. Amosweb.com also offers a good economics dictionary consisting of over 2,000 terms.
The New Palgrave Dictionary of Economics on dictionaryofeconomics.com claims to be an unrivaled resource for a new generation of economists. The Dictionary of Economics includes a number of articles written by Nobel Prize-winning economists such as George Akerlof, Gary Becker and Gerard Debreu. The Economist also publishes an online collection of economic terms and definitions. Amos Web contains a searchable database of over 2,000 economic terms and also offers a layman's guide to the field of economics.