An open letter is a letter that is published in a newspaper or magazine. It is addressed to a particular person but is intended for the general reader, usually in order to protest or give an opinion about something. The Lithuanian parliament also sent an open letter to the United Nations. A published letter on a subject of general interest, addressed to a person but intended for general readership. a letter to an important person, which is printed in a newspaper or magazine, usually in order to protest about something