a connection in a computer, especially a personal computer, to which a new board or card can be added to expand the computer's capabilities.
Origin
1980-85
Examples from the web for expansion slot
The relay board plugs into the expansion slot of the microcomputer and has eight independent relays.
The card usually plugs into a computer's expansion slot.
British Dictionary definitions for expansion slot
expansion slot
noun
1.
a physical electronic interface provided in a computer system to enable extra facilities to be added easily at a later date
expansion slot in Technology
hardware A connector in a computer into which an expansion card can be plugged. The connector supplies power to the card and connects it to the data bus, address bus and control signals of the motherboard. (1998-06-26)