Wikipedia (the on-line free Encyclopedia) defines an atheistic Jew as
"An Atheist Jew is a member of the Jewish community who does not believe in God but still considers himself or herself a Jew. Some Jewish atheists retain customs of the Jewish faith, while others identify as Jewish primarily through ethnic or cultural ties.
Because Jewishness encompasses ethnic as well as religious components, it should be noted that the term "Atheist Jew" does not necessarily imply any kind of contradiction, unlike, for example "Atheist Methodist" or "Atheist Baptist"""Jewish atheism can take both organized and unorganized forms. On the one hand, there is a long tradition of atheistic and secular Jewish organizations, from the Jewish socialist Bund in early twentieth-century Poland to the modern Society for Humanistic Judaism in the United States. Many Jewish atheists feel comfortable within any of the four major Jewish denominations (Orthodox, Reform, Conservative, and Reconstructionist). Again, this presents less of a contradiction than might first seem apparent given even traditional Judaism's emphasis on practice over belief. Much recent Jewish theology makes few if any metaphysical claims and is thus compatible with atheism on an ontological level. The founder of the Reconstructionist movement, Mordechai Kaplan, espoused a naturalistic definition of God, while some post-Holocaust theology has also eschewed a personal God."
