- noun a name used in PCs to represent the first serial port on the computer. There are normally two serial ports, COM1 and COM2, in a PC, although it can support four. Some PCs have a mouse plugged into the first serial port and the modem plugged into the second port.
- The logical name given to the first serial port of a computer. Subsequent ports are COM2, COM3, and so on. Also called COM1 port.