Definition is simple 'Hyperinflation occurs when the government allows inflationary pressure to build up in the economy by printing excessive money, which leads to a gradual rise in the prices of commodities and services'. Today we can see bitcoin for 10k dollars, tomorrow the price of bitcoin can be 20k dollars, in one month 100k. Its like that when you get hit by the economic crash and when government start to print money like crazy, together with new bills, quotations:
`Yugoslavia re-denominated the dinar for the fourth time on 1 October 1993, at a ratio of 1 million to 1. This did not mitigate the hyperinflation, and the 1993 dinar lasted for only three months`
`The 1993 dinar had the largest denomination out of all incarnations of Yugoslavian currency: the banknote, featuring Jovan Jovanović Zmaj had a face value of 500 billion (5×1011) dinara .`
I survived that period, and you can find somewhere information that prices of everything were double every 15h more or less. Today milk is 100, tomorrow its 200 and like that for years. So if this world gets hit by global economic crash fiat money will become worthless.