open letter noun
plural ∼ -ters [count] : a letter that is published in a newspaper but that is addressed to a well-known person or to an organization
▪ In an open letter to the company, a citizens' group implored company executives to reconsider their decision to close the factory.
▪ In an open letter to the company, a citizens' group implored company executives to reconsider their decision to close the factory.
