An apikoros is a Jewish sceptic or apostate.
"apikoros"
It is defined as being a skeptic, or someone who has renounced a religion.
Some do, some do not, but most Atheist Jews do not use the term Apikoros to describe themselves today. Those who do celebrate it usually see it as a symbol of the perseverance of the Jewish people and not a Divine miracle.Some do, because it has (unfortunately) been commercialized in the Western world and some also identify it as just part of the Gentile holidays. To some, its original message of serving God and fighting Hellenistic assimilation, has been all but forgotten.