From the second edition (1989):
(dɪˈstəʊpɪə) [mod.L., f. dys- + U)topia.]

An imaginary place or condition in which everything is as bad as possible; opp. Utopia (cf. Cacotopia). So dysˈtopian n., one who advocates or describes a dystopia; dysˈtopian a., of or pertaining to a dystopia; dysˈtopianism, dystopian quality or characteristics.

1868 J. S. Mill in Hansard Commons 12 Mar. 1517/1 It is, perhaps, too complimentary to call them Utopians, they ought rather to be called dys-topians, or caco-topians. What is commonly called Utopian is something too good to be practicable; but what they appear to favour is too bad to be practicable. 1952 Negley & Patrick Quest for Utopia xvii. 298 The Mundus Alter et Idem [of Joseph Hall] is‥the opposite of eutopia, the ideal society: it is a dystopia, if it is permissible to coin a word. 1962 C. Walsh From Utopia to Nightmare 11 The ‘dystopia’ or ‘inverted utopia’. Ibid. 12 Stories‥that seemed in their dystopian way to be saying something important. Ibid. ii. 27 A strand of utopianism or dystopianism. 1967 Listener 5 Jan. 22 The modern classics—Aldous Huxley's Brave New World and George Orwell's Nineteen Eighty Four—are dystopias. They describe not a world we should like to live in, but one we must be sure to avoid. 1968 New Scientist 11 July 96/3 It is a pleasant change to read some hope for our future.‥ I fear that our real future is more likely to be dystopian.