Derogatory clause is a sentence of secret character inserted by a testator in his/her will containing a provision that any later will not having that precise clause is invalid. The testator alone will have knowledge of the clause. S/he reserves the secret with him. Derogatory clause is incorporated in a will as a precautionary measure to protect against a later will extorted by undue influence, duress, or violence. A subsequent will made without including the derogatory word is void.
It also refers to a statutory or contractual provision proclaiming that the document in which it appears, or a part of the document, cannot be repealed or amended. Such provisions are usually considered ineffective.