From Longman Dictionary of Contemporary Englishexpansion slotexˈpansion ˌslot noun [countable] a place on a computer system circuit board that can hold an expansion card
Examples from the Corpus
expansion slot• The card fits into a free expansion slot on the motherboard.• It is very important to have the greatest possible support around the expansion slot area.From Longman Business Dictionaryexpansion slotexˈpansion ˌslot noun [countable]COMPUTING a CONNECTOR on a computer system board that can hold an expansion cardInternal modems fit into an expansion slot and don’t require a serial port socket. 