Definition of "shibboleth"

In recent times, the correct treatment of initial h in speech has come to be regarded as a kind of shibboleth of social position.

1933, “H”, in Oxford English Dictionary

He also declares that "th" is the veritable English shibboleth. He advises those Germans who cannot pronounce the sound correctly to pronounce it like "d," the symbol which he regularly uses for "th" in his lessons.

1922, Pennsylvania-German Society, The Pennsylvania-German Society, page 110

The teacher says he must stick largely to the old methods and cling to the old shibboleths or he will naturally get bad results in the examination. Only much practice along the lines the examination is going to follow will insure a [success].

1924, Modern Languages, page 112

I pose the iconoclastic suggestion that even at this late stage in B.R. dieselisation, rigid standardisation might be a shibboleth.

1964 May, R. & M., “What chance for an outstanding prototype?”, in Modern Railways, page 319

The truth is that I found success by stumbling off alone in a direction most people thought was a dead end, breaking all the 1990s shibboleths about children’s books in the process.

2019 January 11, Tina Jordan, quoting J. K. Rowling, “Some Dos and Don’ts From Famous Writers”, in New York Times‎

Yet LBJ was very much a product of the Cold War, believing its shibboleths about communist conquest being irreversible and requiring worldwide containment even when a country, such as Vietnam, that might be falling to the communists did not threaten US national interests.

2022, Gary Gerstle, chapter 2, in The Rise and Fall of the Neoliberal Order […] , New York: Oxford University Press, Part I. The New Deal Order, 1930–1980