A supply shock is an event that suddenly increases or decreases the supply of a commodity or service, or of commodities and services in general. This sudden change affects the equilibrium price of the good or service or the economy's general price level.
In the short run, an economy-wide negative supply shock will shift the aggregate supply, decreasing the output and increasing the price level.
In the short run, an economy-wide positive supply shock will shift the aggregate supply, increasing output and decreasing the price level.