It is said of a type of telephone call from an unknown number, in which when you pick up there is a silence and perhaps (although not always) after a few seconds, a brief word of farewell. They are telephone calls executed by automated telemarketer robots for this purpose, and they are the prelude to a call from a person, who will finally be in charge of executing the commercial operation to convince you to buy, acquire a product or adhere to an offer.
