1. (I/O port) A connection point with associated control circuitry that allows I/O devices to be connected to the internal bus of a microprocessor. See also parallel port, serial port, communication port.
2. A point through which data can enter or leave a network, either on the network or the DTE (computer) interface.
3. To move software from one type of computer system to another, making any necessary changes en route. In a simple case little more than recompilation may be required, while in extreme cases the software might have to be entirely rewritten.