Karl Popper used the term in his influential book The Poverty of Historicism, to mean: "an approach to the social sciences which assumes that historical prediction is their primary aim, and which assumes that this aim is attainable by discovering the 'rhythms' or the 'patterns', the 'laws' or the 'trends' that underlie the evolution of history" (p. 3, italics in original).
Most recently, Historicism has been used by post-modernist thinkers to describe the view that there is no absolute truth about deep philosophical questions that should stand for all time. Instead, historicism holds that there is only the history of philosophy or more generally, intellectual history, including the history of science and technology'. This sense is sometimes termed New Historicism.
The historicist position is that there is no objective way to determine which of the various competing theories on a subject is correct. In science, philosophy, or any other discipline, there are only the facts about who has believed what, and when they believed it. Therefore, historicists can accept Hegel's famous catchphrase, "Philosophy is the history of philosophy."
Finally, the term is used by some Christian fundamentalists to refer to that form of Biblical exegesis which holds that the Bible is able to tell us about events in the future, especially the supposed "end times".
Elements of all three of these definitions can be found in the extensive writings of G.W.F. Hegel, one of the most influential philosophers of Nineteenth Century Europe.