This article explores the concept of political diglossia, a phenomenon arising in totalitarian or semitotalitarian countries, where the language of official propaganda gives rise to its opposite: the unofficial, underground language of antipropaganda. The author studies one semantic domain – the colloquial designations of the political police and security forces in contemporary Poland – and compares them with the official designations. The semantics of the relevant words and expressions is studied in great detail so that the social attitudes encoded in them can be revealed and rigorously compared. To achieve this, the author relies on the natural semantic metalanguage that she has developed over the last two decades, which has already been applied in the study of many other semantic domains, in many different languages. The social and political attitudes encoded in the Polish expressions referring to the security apparatus are discussed against the background of Poland's history. The author shows that language is not only the best “mirror of mind” (Leibniz) and “mirror of culture” and “guide to social reality” (Sapir), but also a mirror of history and politics. (Sociolinguistics, pragmatics, semantics, language of propaganda, expressive language)