A state of the economy resulting from an extended period of negative economic activity as measured by GDP. It is often described as a more severe form of a recession that leads to extended unemployment, a spike in credit defaults, broad declines in income and production, currency devaluation and a deflationary economy.
I know that the Great Depression was the longest and most severe depression ever experienced by the industrialized Western world, sparking fundamental changes in economic institutions, macroeconomic policy, and economic theory.
I think that will help you I hope it does. : )