A clandestine item or mode of attack unknown to the enemy. The term came into wide use during World War II, when it was rumored that Hitler was going to launch a powerful secret weapon against Great Britain. Subsequently the term was applied to pilotless planes, robot bombs, rockets, and nuclear bombs. Thereafter it entered the civilian vocabulary, where it is used in sports (“Bill’s second serve, stronger than the first, is his secret weapon”) and numerous other activities. Edith Simon had it in The Past Masters (1953): “See the candid camera at work, that misnamed secret weapon.”

Also, WMD. Weapons that can greatly harm or kill large numbers of people and/or severely damage man-made structures or the biosphere. The term was first used by the Archbishop of Canterbury in 1937 with reference to the aerial bombardment of Guernica, Spain. Less than a decade later, the term was applied to nonconventional weapons, specifically nuclear weapons. During the Cuban missile crisis of 1962, the term was used by President John F. Kennedy, referring to nuclear missiles. Fearing Iraq’s use of nuclear weapons, the alleged existence of such weapons became the main justification for the 2003 invasion of that country. By then, the term was so well known and so often abbreviated that it was on its way to clichédom.