extremely large in area, size, amount, etc. synonym huge a vast area of forest a vast crowd a vast amount of information At dusk bats appear in vast numbers. His business empire was vast. In the vast majority of cases, this should not be a problem. Your help made a vast difference. We’ve hired a marquee at vast expense. Word Origin late Middle English: from Latin vastus
‘void, immense’.Extra examples In the vast majority of cases this should not be a problem. There is a vast amount of information available online. To the south lay a vast area of wilderness. Vast crowds lined the route of the marathon. We’ve hired a marquee at vast expense.