UUCP stands for 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. Specifically, uucp is one of the programs in the suite; it provides a user interface for requesting file copy operations. The UUCP suite also includes uux (user interface for remote command execution), uucico (communication program), uustat (reports statistics on recent activity), uuxqt (execute commands sent from remote machines), and uuname (reports the uucp name of the local system).

Although UUCP was originally developed on and is most closely associated with Unix, UUCP implementations exist for several other operating systems, including Microsoft's MS-DOS, Digital's VAX/VMS, Commodore's AmigaOS, and Mac OS.

.uucp was a pseudo-domain-style suffix used in the late 1980s when identifying a hostname not connected directly to the Internet but possibly reachable through inter-network gateways. In this case, it indicated that the hostname preceding it was reachable by UUCP networking. This was one of several apparent "top-level domains" that were not actually in the Internet root, but were sometimes used in addresses during the time when non-Internet networks remained in wide use.

As UUCP hosts were not always uniquely named, and there was no official global table listing them (though the UUCP Mapping Project was an informal effort to create such a list), actual access to one (e.g., for routing e-mail to it) required the use of a full bang path, which did not follow domain-name-style syntax, unless the particular software being used had been programmed to recognize particular hostnames in a domain style and route to them.