To imprecate means to curse someone — to invoke evil upon a person. So, an imprecation is the act of imprecating. In The Red Badge of Courage, a group of soldiers charges into enemy territory, but then the men hesitate. Suddenly, "the roar of the lieutenant" brings the men back to reality. The lieutenant cajoles and curses the men into action: "Come on," he was shouting. The men stared with blank and yokel-like eyes at him. He was obliged to halt and retrace his steps. He stood then with his back to the enemy and delivered gigantic curses into the faces of the men. His body vibrated from the weight and force of his imprecations. And he could string oaths with the facility of a maiden who strings beads.