All terms
An uncollateralised loan that must be borrowed and repaid in a single transaction.
Because a blockchain transaction either fully succeeds or fully reverts, you can borrow millions with no collateral as long as you repay within the same transaction. If you cannot, the whole thing unwinds as if it never happened.
This enables legitimate arbitrage and refinancing. It also gives attackers enormous temporary capital to manipulate thin markets.
Many DeFi exploits use flash loans to move an oracle price, borrow against the distortion, and exit in one transaction.
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More defi terms
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