From Longman Dictionary of Contemporary Englishtest cardˈtest card noun [countable] British English AMTa pattern or picture that is shown on television when there are no programmes
Examples from the Corpus
test card• This apparently involves sending patients an eyesight test card and then running through the test itself over the telephone.• Each strip is viewed in turn, starting at the end where the light test card is positioned.• The object is to determine in which of sixteen horizontal strips the lower edge of the test card lies.• The edge of the test card is where the first strip contains only background.• He was sprawled on the floor, watching the innocent little girl on the test card with a touching devotion. 