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Related to grandfather: Grandfather paradox
A clause that exempts certain people or businesses from new limitations or restrictions, thus allowing them to continue doing or benefiting from something as they did before. Originally referred to a clause added to the constitutions of some Southern US states that exempted people with relatives that had voted before 1867 from strict new voting requirements, in effect disproportionately limiting the ability of African Americans to vote. No, I still get to pay the reduced rate, thanks to a grandfather clause in my contract.
To exempt certain people or businesses from new limitations or restrictions, thus allowing them to continue doing or benefiting from something as they did before. This can be done through the use of a "grandfather clause." A noun or pronoun can be used between "grandfather" and "in." If they change the pension plan, they better grandfather us in!
(a) grandfather clause
a clause in an agreement that protects certain rights granted in the past even when conditions change in the future. The contract contained a grandfather clause that protected my pension payments against claims such as might arise from a future lawsuit.
grandfather someone or something in
to protect someone or a right through the use of a grandfather clause. My payments were grandfathered in years ago.