Also at one fell swoop. All at once, in a single action, as in This law has lifted all the controls on cable TV in one fell swoop. This term was used and probably invented by Shakespeare in Macbeth (4:3), where the playwright likens the murder of Macduff's wife and children to a hawk swooping down on defenseless prey. Although fell here means "cruel" or "ruthless," this meaning has been lost in the current idiom, where it now signifies "sudden."