1. A word or pronunciation that distinguishes members of one group from another. This meaning comes from the biblical story in Judges 12:5-6 where the Ephraimites were unable to pronounce the word "shibboleth" correctly, betraying their identity and leading to their demise.
This definition often signifies a distinguishing feature, characteristic, or belief that separates groups, often in a discriminatory or prejudiced way.
For example, "Wearing a certain brand of clothing is a shibboleth of belonging to a particular social group."
2. A password or other secret phrase used for identification or authentication. This meaning is more modern and stems from the original meaning of a distinguishing feature.
For example, "The website uses a shibboleth to verify users' identities."
So, depending on the context, "shibboleth" can mean something that distinguishes a group or a secret phrase for identification.