From the second edition (1989):
(ˈgəʊldwɪnɪz(ə)m) [f. the name Goldwyn + -ism.]

A witticism uttered by or typical of Samuel G. Goldwyn, American film producer (1882–1974), esp. one that revolves round a contradiction, a colourful image, etc.

1937 Sat. Evening Post 8 May 82/2 ‘It sounds like Sam Goldwyn.’ Chaplin said, ‘We'll pin it on Sam,’ and he repeated it until it became a world-famous Goldwynism. Ibid., A kind of Goldwyn scholarship has grown up; there are specialists who can detect fake Goldwynisms as an archeologist can spot a phony Greek vase. 1938 I. Goldberg Wonder of Words xii. 245 In a phrase that has become humorously popular, and that has been attributed to the moving-picture producer Sam Goldwyn, renowned for his so-called Goldwynisms, the ideas of exclusion and inclusion have been telescoped. ‘Include me out!’ he is said to have exclaimed. 1959 Globe & Mail (Toronto) 24 Sept. 34/1 A Goldwynism‥is a slight twisting of a word or a slight misstatement that makes an ordinary remark sound wittily off-beat. 1967 Sunday Mail (Brisbane) 13 Aug. 30 He [sc. S. Goldwyn] gave a new word to the English language: Goldwynism, meaning those delightful malapropisms such as: ‘in two words—impossible’, ‘verbal contracts are not worth the paper they're written on’, and ‘I'll give you a definite maybe’. 1969 Daily Tel. 5 Nov. 17/3 He will be remembered as the master of innumerable Goldwynisms, many of which, he says, were invented by comedians and pinned on him.