Wiktionary
n. (context business finance English) The buying of commodities or other assets earlier than normal, or in quantities greater than normal, because of rumours of coming shortages or price rises.
Wikipedia
Panic buying is the act of people buying unusually large amounts of a product in anticipation of or after a disaster or perceived disaster, or in anticipation of a large price increase or shortage, as can occur before a blizzard or hurricane or government decree banning a particular popular product such as incandescent light bulbs. These goods are bought in large amounts to offset a potential shortage or as an act of safety. While panic buying can result in a sudden increase in the cost of goods, it is distinct from looting as it does not entail theft or deliberate property damage.
Usage examples of "panic buying".
Gasoline shortages, panic buying, mile-long lines at service stations.
There had been no major problems with the townsfolk themselves, beyond an initial run of panic buying which the town's mayor brought to a halt by a quick and decisive order to close all the stores.
There was a hurried wave of panic buying and the black market was booming just as much as ever.