The situation where the equilibrium level of real GDP falls short of potential GDP is known as

In macroeconomics, the output gap is the difference between an economy's actual real GDP and its potential GDP [3]. When the equilibrium level of real GDP falls below the potential GDP, it is specifically defined as a recessionary gap. This situation, also known as a negative output gap, indicates that the economy is underperforming or in a downturn, often characterized by 'slack' or excess supply and domestic resource utilization below sustainable levels [3]. During such periods, actual output drops below the economy's full capacity or production capacity [2]. Conversely, an inflationary gap (or positive output gap) occurs when actual real GDP exceeds potential GDP, typically leading to upward pressure on prices [2]. Therefore, the scenario where real GDP falls short of potential GDP is a recessionary gap.

Sources

1. [2] https://www.imf.org/external/pubs/ft/fandd/2013/09/basics.htm
2. [3] https://www.khanacademy.org/economics-finance-domain/ap-macroeconomics/national-income-and-price-determinations/equilibrium-in-the-ad-as-model-ap/a/lesson-summary-equilibrium-in-the-ad-as-model