3 meanings.

(1) An interface on a computer to which you can connect a device. Personal computers have various types of ports. Internally, there are several ports for connecting disk drives, display screens, and keyboards. Externally, personal computers have ports for connecting modems, printers, mice, and other peripheral devices.

Almost all personal computers come with a serial RS-232C port or RS-422 port for connecting a modem or mouse and a parallel port for connecting a printer. On PCs, the parallel port is a Centronics interface that uses a 25-pin connector. SCSI (Small Computer System Interface) ports support higher transmission speeds than do conventional ports and enable you to attach up to seven devices to the same port.

(2) In TCP/IP and UDP networks, an endpoint to a logical connection. A number that is shown in a URL, following a colon right after the domain name (e.g. http://www.example.com:80). The port number identifies what type of port it is. Every service on an Internet server "listens" on a particular port number. Most of these services have standard port numbers. Web servers normally listen on port 80, and the standard Gopher port is 70. Services can also listen on nonstandard ports, in which case the port number must be specified in a URL when the server is accessed.

(3) (verb) To move a program from one type of computer platform to another ( such as from a Windows program to one on a Macintosh.). To port an application, you need to rewrite sections that are machine dependent, and then recompile the program on the new computer. Programs that can be ported easily are said to be portable.