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onion routing

n. (context computing English) A technique for anonymous communication over a computer network, the messages being repeatedly encrypted and sent through nodes called ''onion routers'' that perform only one stage of the decryption.

Wikipedia
Onion routing

Onion routing is a technique for anonymous communication over a computer network. In an onion network, messages are encapsulated in layers of encryption, analogous to layers of an onion. The encrypted data is transmitted through a series of network nodes called onion routers, each of which "peels" away a single layer, uncovering the data's next destination. When the final layer is decrypted, the message arrives at its destination. The sender remains anonymous because each intermediary knows only the location of the immediately preceding and following nodes.