at one fell swoop

All at once, with a single decisive or powerful action. When the economy crashed, thousands lost their jobs, their homes, and their pensions at one fell swoop.

A single decisive or powerful action. When the economy crashed, thousands lost their jobs, their homes, and their pensions in one fell swoop. With one fell swoop, the military junta arrested the prime minister, executed its enemies in parliament, and assumed total control of the country.

Fig. in a single incident; as a single event. (This phrase preserves the old word fell, meaning "terrible" or "deadly.") The party guests ate up all the snacks at one fell swoop. When the stock market crashed, many large fortunes were wiped out in one fell swoop.

A single operation, often a violent one. This term was coined by Shakespeare, who used the metaphor of a hell-kite (probably a vulture) killing chickens for the murder of Macduff’s wife and children: “Oh, Hell-Kite! All? What, all my pretty chickens and their dam at one fell swoop?” (Macbeth, 4.3). The adjective fell was Old English for “fierce” or “savage.”

A single and rapid act. “Fell” comes from an Old English word for frightful and “swoop” describes the way hawks and other birds of prey drop out of the sky to capture their victims. Accordingly, something that is done “in one fell swoop,” whether or not it is awful, happens with no hesitation. Shakespeare coined the phrase in Macbeth, where the character Macduff laments the murders of his wife and children with “What, all my pretty chick- ens and their dam / At one fell swoop?”