noun | ahy-oh-yoo
An IOU is like the crypto world's version of a handshake deal - it's a promise to pay someone back in the future, but without any of that pesky legal paperwork or collateral. It's the ultimate expression of trust between two parties, or the ultimate recipe for disaster, depending on how you look at it.
Example
"I lost all my BTC in a boating accident, so I had to give my dealer an IOU for the next shipment. Fingers crossed he doesn't break my kneecaps before I can come up with the cash!"
"IOUs are like the 'thoughts and prayers' of the financial world - they're a nice gesture, but they don't actually do anything to solve the underlying problem. If you're relying on an IOU to get paid back, you might as well be hoping for a leprechaun to ride in on a unicorn and deliver you a pot of gold."