a. A religious movement, which orig. became active among various Protestant bodies in the United States after the war of 1914–1918, based on strict adherence to certain tenets (e.g. the literal inerrancy of Scripture) held to be fundamental to the Christian faith; the beliefs of this movement; opp. liberalism and modernism.

1923 Daily Mail 24 May 8 Mr. William Jennings Bryan..has been exerting the full force of his great eloquence in a campaign on behalf of what is termed ‘Fundamentalism’. 1925 K. LAKE Relig. Yesterday & Tomorrow 63 There has been in America some surprise at the sudden rise of Fundamentalism in the last five years. 1927 Observer 5 June 5/3 Fundamentalism and the Klux Klan are signs of alarm on behalf of the older ideals. 1955 Times 25 Aug. 14/1 ‘Fundamentalism’..appears to have been used first in connexion with the (American) Northern Baptist Convention of 1920 to describe the more conservative delegates who desired ‘to restate, reaffirm, and re-emphasize the fundamentals of our New Testament faith’.Ibid., Now ‘fundamentalism’..appears to describe the bigoted rejection of all Biblical criticism, a mechanical view of inspiration and an excessively literalist interpretation of scripture.

b. In other religions, esp. Islam, a similarly strict adherence to ancient or fundamental doctrines, with no concessions to modern developments in thought or customs.

1957 L. BINDER in Middle East Jrnl. XI. 391 Fundamentalism in religion and the Hinduization of the national historical myth were made possible [in India] the historical and religious work of Europeans. 1961 Relig. & Politics in Pakistan ii. 52 These same circumstances determined that the Congress act as midwife at the birth of Islamic fundamentalism in the Khilafat movement. 1981 Observer 27 Sept. 32/1 The new, or rather very old, Islam, the dangerous fundamentalism revived by the ayatollahs and their admirers. 1984 Church Times 2 Mar. 6/1 The newly-revived Western Christian awareness of ‘Islamic fundamentalism’, whose symbolic figure is Ayatollah Khomeini. 1984 Times 27 Apr. 13/2 It is this very process that has helped ignite the fires of Sikh fundamentalism, rather as Shiite fundamentalism was sparked off by the forces of modernization in Iran.

So fundamentalist, an adherent of fundamentalism; also, an economic or political doctrinaire. Also attrib. or as adj., and transf.1922 Contemp. Rev. July 20 The fundamentalist creed. Ibid. 21 The Fundamentalists have been fortunate in their non-ministerial leader [sc. W. J. Bryan]. 1925 K. LAKE Relig. Yesterday & To-morrow 60 The most, but the least well educated, is the Fundamentalist. Ibid. 62 The Fundamentalists have zeal, but it is certainly not according to knowledge. 1926 H. F. OSBORN Evol. & Relig. in Educ. 12 The fundamentalist movement..sought to re-establish the Biblical literalism of the time of Cromwell, Milton, and the Puritans. 1955 Times 25 Aug. 14/1 The dangers of the new fundamentalist movement. One of the encouraging developments for Christian teachers to-day is the new relationship which is growing up between scientific and religious thought. 1957 Middle East Jrnl. XI. 391 Less well known is their [sc. Europeans'] part in the development of non-Christian fundamentalist movements through their translations..of the ancient sources. 1961 L. BINDER Relig. & Pol. in Pakistan xiii. 378 The fundamentalist movement is a lower middle-class movement..oriented to the institutions of a..passing age. 1961 WEBSTER, Fundamentalist, an extreme conservative; esp: one who attacks any deviation from certain doctrines and practices he considers essential (as to a religious, political, or educational system). 1969 New Yorker 14 June 45/1 I've never been a flashy stylist, like Arthur. I'm a fundamentalist. Arthur is a bachelor. I am married and conservative. 1973 Economist 15 Dec. 106/2 The fundamentalists look at a company's product, balance sheet, record and management before deciding whether the stock market has put the right value on the shares. 1981 Times 26 Sept. 4/2 The measures are designed mostly to curb the influence of Muslim fundamentalists. 1985 Daily Tel. 29 Mar. 22/4 Fundamentalist Jews are limbering up to oppose the plan on the grounds that it will depict scenes from the New Testament as well as the Old.