Firehose of falsehood is a term used to describe a situation where a lot of false information is spread quickly and widely. It is like a fire hose spraying out water – it can spread a lot of false information very quickly. It is most often used to refer to dangerous false information that is put out on the internet or in the news. This false information is often spread by people or groups who want to confuse people or manipulate them for their own gain. By spreading false information, these people can cause panic and make people believe things that aren't true.