Mixer

Virtual currency
Mixer (also called laundry service and tumbler) is

"a type of anonymiser that obscures the chain of transactions on the blockchain by linking all transactions in the same bitcoin address and sending them together in a way that makes them look as if they were sent from another address. A mixer or tumbler sends transactions through a complex, semi-random series of dummy transactions that makes it extremely difficult to link specific virtual coins (addresses) with a particular transaction. Mixer services operate by receiving instructions from a user to send funds to a particular bitcoin address. The mixing service then "comingles" this transaction with other user transactions, such that it becomes unclear to whom the user intended the funds to be directed."