Stagnation occurs when high inflation combines with

Low economic growth

Explanation:

Stagflation is a situation of slow economic growth and relatively high unemployment (which basically means that aggregate production is reducing and some of the imputs of the economy, such capital or labor, are unemployed) ,  accompanied by rising prices, or inflation. In terms of national accounting, it means a reduction in gross domestic product (GDP), with inflation (rise in all prices in the economy).In terms of aggregate demand and supply models, stagnation is the result of a contraction of aggregate supply, which ceteris paribus, results in lower levels of production and higher prices.Many theories have tried to explain this fenomena. Commun interpretations link stagnation with and increase of the cost of production in the economy (that might be generated by an increse of gasoline for example), and its implications in the production (lower production because of higher costs), consequently unemployment and a rise of prices due to the increase of cost.