Answer:
Hyperinflation.
Explanation:
Hyperinflation occurs, according to economist Phillip D. Cagan, who developed the most widely accepted mathematical model of hyperinflation to this day, when the general price level in a economy increases by 50% in a single month.
The cause of hyperinflation is clear: an excessive growth of the money supply that is not accompanied by a smiliar growth in the output of the economy. The most common reason for this is governments printing money to meet spending demands.
This is exactly what happened in Zimbabwe: the government of former ruler Robert Mugabe was broke, and Mugabe resorted to printing money to pay for debts, for the military, among other things.