"Orwellian" is an adjective describing a situation, idea, or societal condition that George Orwell identified as being destructive to the welfare of a free and open society. It denotes an attitude and a brutal policy of draconian control by propaganda, surveillance, misinformation, denial of truth (doublethink), and manipulation of the past, including the "unperson"--a person whose past existence is expunged from the public record and memory, practised by modern repressive governments. Often, this includes the circumstances depicted in his novels, particularly Nineteen Eighty-Four but political double-speak is criticized throughout his work, such as in Politics and the English Language.
There has also been a great deal of discourse (John Rodden, Christopher Hitchens et al), on the possibility that Orwell galvanized his ideas during his experience of oppression, and his subsequent writings in the English press, during the Spanish Civil War. Orwell was a member of the Workers' Party of Marxist Unification (POUM) militia and suffered suppression and escaped arrest by the Comintern faction working within the Republican Government. Following his escape he made a strong case for defending the Spanish revolution from the Communists there, and the mis-information in the press at home. During this period he formed strong ideas about the reportage of events, and their context in his own ideas of imperialism and democracy.
Orwell's anti-Comintern stance often brought him into conflict with literary peers such as W.H. Auden and Stephen Spender; as well as 'left-wing' commentators such as Anne Murray, Duchess of Atholl. This, in turn, gave Orwell a sense that what he was hearing from his peers on Spain was 'political partisanship' (Time and Tide, 16 July 1938). A partisanship that Thomas Cushman and ?John Rodden have argued that Orwell was inoculated against during his time as an Imperial Policeman in Burma.
Consequently Orwell was unable to reconcile either his own 'truth', that of imperial Britain, or his compatriots in the 'left-wing' press; and thus he satirised this propagandic paradigm in his novel Nineteen Eighty-Four.