Countermand
Categories: Regulations
In general, it means to revoke an order. As in, "Col. Wilkins countermanded Sgt. Thompson's order to assault Hill 45, because it turned out those were, um...our troops on Hill 45."
Financially speaking, it can refer to an order to stop payment. As in, "Countermand that check! It turns out that Mme. Crystal doesn't have psychic power after all!"