Real Dictionary

grandfather clause in American English
a former law in some Southern states waiving electoral literacy requirements for those whose forebears voted before the Civil War, thus keeping the franchise for illiterate whites
noun: a clause in the constitutions of some Southern states after 1890 intended to permit White people to vote while disfranchising Black people: it exempted from new literacy and property qualifications for voting those men entitled to vote before 1867 and the

grandfather clause in British English
noun: a clause in the constitutions of several Southern states that waived electoral literacy requirements for lineal descendants of people voting before 1867, thus ensuring the franchise for illiterate White people: declared unconstitutional in 1915