The business cycle or economic cycle is the downward and upward movement of gross domestic product (GDP) around its long-term growth trend. The length of a business cycle is the period of time containing a single boom and contraction in sequence. These fluctuations typically involve shifts over time between periods of relatively rapid economic growth (expansions or booms), and periods of relative stagnation or decline (contractions or recessions).
Business cycles are usually measured by considering the growth rate of real gross domestic product. Despite the often-applied term cycles, these fluctuations in economic activity do not exhibit uniform or predictable periodicity.
CBO Glossary of Budgetary and Economic Terms (July 2016)
Fluctuations in overall economic activity that are characterized by swings in real gross domestic product, real income, employment, and industrial production. Over a business cycle, real activity rises to a peak (its highest level during the cycle) and then falls until it reaches a trough (its lowest level following the peak), whereupon it starts to rise again, defining a new cycle. Business cycles are irregular, varying in frequency, magnitude, and duration. See recession.