Hit·ler (h?t?l?r), Adolf Known as “Der Führer.” 1889-1945. Austrian-born leader of the German Nazi Party (1921-1945) and chancellor of the Third Reich (1933-1945). His fascist philosophy, embodied in Mein Kampf (1925-1927), attracted widespread support, and after 1934 he ruled as an absolute dictator. Hitler’s pursuit of aggressive nationalist policies resulted in the invasion of Poland (1939) and the subsequent outbreak of World War II. His regime is infamous for the extermination of millions of people, especially European Jews. He committed suicide when the collapse of the Third Reich was imminent (1945).Hit·ler?i·an (h?t-lîr??-?n) adj.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.