Expansion Slot

Definition: An expansion slot usually refers to any of the slots on a motherboard that take PCIe, PCI, AGP, ISA, or other format expansion cards.

Sometimes the openings on the rear of the case are referred to as expansion slots.

A typical warning to someone before installing a new expansion card is "Make sure you have a free expansion slot!"

Examples: "My newer motherboard contains a number of PCIe expansion slots."