Bitcoin mixer
Bitcoin mixer is software (or a service like CoinJoin) that accepts Bitcoin from multiple users, mixes them so you can’t identify who sent how much, and then sends out different bitcoins to their destinations.
If you were to view such a transaction on an explorer, you’d find the address of the mixer as the recipient (in the case of an outgoing transaction from your wallet) instead of a Bitcoin address. Similarly, if you typed in a transaction recipient’s address, and looked to see where the coins came from, all you’d find would be the tumbler’s address.
It’s called a “mixer” because it mixes your coins with other holders' coins to the point that none of them can be connected back to their original wallet addresses.
Hence, when you use this solution, you can send Bitcoin or receive it while remaining completely anonymous.
These anonymous transactions aren’t always free. Some of these Bitcoin tumblers require you to pay service fees for mixing your coins.