Unutterably opposed. This Americanism probably comes from industry, where a machine is said to be dead set when it is fastened so that it cannot be made to move. The transfer to firm resolve or hostility against some person, course of action, and so on, was made by the early nineteenth century. “A dead set is to be made from various quarters against the abominable innovation of publishing Divisions by authority” (General P. Thompson, 1836).