What is an appeal (in verification of a statement made) to a superior sanction, in such a form as exposes the party making the appeal to an indictment for perjury if the statement be false called?

oath — (Law) An appeal (in verification of a statement made) to a superior sanction, in such a form as exposes the party making the appeal to an indictment for perjury if the statement be false. (Webster's 1913.)