The word d’Oh! can be described as Expressing frustration at the realization that things have turned out badly and cites the cartoon The Simpsons in setting both its definition and its spelling (OED s.v. D’oh). A dictionary attempting to set rather than describe usage would be very unlikely to include a word made famous by a television cartoon. Furthermore, the policy of the Oxford English Dictionary board itself describes the resource as descriptive rather than prescriptive. In its Guide to the Third Edition of the OED the board writes that the Dictionary is intended to be descriptive, not prescriptive, though the dictionary notes that it will indicate when usages have been popularly considered incorrect (OED Online). Noting a usage as being popularly incorrect does not make the resource prescriptive, however: it simply describes the popular usage of the word.
Oxford English Dictionary Description