From Longman Dictionary of Contemporary Englishtop-up cardˈtop-up ˌcard noun [countable] a card that you buy in order to be able to continue using a pay-as-you-go mobile phoneFrom Longman Business Dictionarytop-up cardˈtop-up card a small card or piece of paper you can buy which increases the amount of time that you have for making calls with your mobile phone → card
