UUCP is an abbreviation of Unix-to-Unix Copy. The term generally refers to a suite of computer programs and protocols allowing remote execution of commands and transfer of files, email and netnews between computers.

The name uucp was a pseudo-domain-style suffix used in the 1980s when identifying a hostname not connected directly to the Internet, but possibly reachable through other inter-network gateways. The suffix was appended to a UUCP bang path separated with a dot, e.g., host1!host2!host3.uucp. The suffix prevented messages from being routed via the Simple Mail Transfer Protocol (SMTP) in mail exchangers, and it indicated that the hostname preceding it was reachable by UUCP networking. It was not a top-level domain in the Domain Name System (DNS) root.