Double Spend Definition: Double spend refers to the risk of a cryptocurrency being used more than once, allowing a person to reclaim coins that were already spent as theirs. This situation is possible when a transaction’s information is changed within a blockchain when specific criteria are met.
When modified blocks change the blockchain when they are altered, this allows double spending to occur. Cryptocurrencies that are not well protected in cold storage or a secure wallet are more likely to be at risk for double spending, which is essentially theft. Testing a platform may uncover weaknesses that make double-spending possible, and this could be done during a 51% attack, which is one of the most common methods.