curfew; lights-out order
Rare term referring to an official order to turn off lights, often in a military or institutional context. Not the common word for a general curfew (外出禁止令).
During the war, a lights-out order was issued and the town went completely dark.
Compound of 消灯 (しょうとう, 'turning off lights') and 令 (れい, 'order, command').