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.
if you do something at one fell swoop, you do everything you have to do at the same time I'd prefer to do the paperwork in one fell swoop. At least then we know it's finished with.