What term did Gertrude Stein use to describe Hemingway's generation?

Gertrude Stein used the term “Lost Generation” to describe Hemingway’s generation.

The phrase referred broadly to people who came of age during or just after the First World War, especially the American writers and artists living in Paris during the 1920s. Stein is credited with popularizing the expression in conversation with Hemingway, reportedly repeating a French garage owner’s criticism of young mechanics: “You are all a génération perdue.” She then applied the idea to the young people shaped by the war.

Hemingway helped make the phrase famous by using it as an epigraph for The Sun Also Rises, published in 1926: “You are all a lost generation.” The novel portrays expatriates struggling with disillusionment, restlessness, damaged relationships, and the difficulty of finding purpose after the war. Other writers commonly associated with the Lost Generation include F. Scott Fitzgerald, John Dos Passos, and Ezra Pound.

A subtle point is that Hemingway did not wholly accept the label’s pessimism. He later suggested that his characters were battered rather than permanently lost. “Jazz Age” describes the 1920s cultural era, while “Greatest Generation” refers to a later cohort.