Ye Olde Glossary

- Apikoros: Heretic, apostate, etc. I recently read a haredi children's book that said anyone who doesn't believe that the Torah wasn't communicated, word-for-word and letter-for-letter, from God to Moses, is an apikoros. It showed a picture of a Neanderthal with a briefcase (his name was Dr. Stonewall or something) trying to teach evolution to yeshiva boys. I find this hilarious.

- Gehenna: Jewish Hell. More complicated than that, but I'm lazy right now.

- Gilgul: Jewish reincarnation.

- Halakha (Halakha, Halakhah, etc.): Jewish law. For Orthodox Jews, this means the 613 mitzvot as determined by the Torah, Talmud, tons of other rabbinical exegesis, and whatever their own personal sage determined last week. Theoretically authoritative to all Orthos; in practice somewhat more open to interpretation.

- Hasidic: The "mystical" camp of modern Haredi society. (As opposed to Misnagdic.)

- Haredi: More neutral term for Ultra-Orthodox, which is seen as alternately perjorative or ridiculous (Jon Stewart- "Ultra-Orthodox Jews are regular Jews who achieve Ultra-Orthodox powers via a radioactive yarmulke incident"). More commonly used in Israel than the US, though it is catching on here.

- Mishnah: Part of the Talmud. Jewish oral law supposedly communicated from God to Moses to... well, after that it gets fuzzy.

- Mitzvot (sing., mitzvah): Commandment.

- Rebbe: Leader of a Hasidic sect/community. Not the same thing as a rabbi, who is highly educated in matters of Jewish law. (Though most rebbes today are also rabbis).

- Talmud: Super-long compilation of rabbinic commentary on Jewish law. Also has tons of cool stories (called Aggadah or Aggadot). Predictably, the stories get less official coverage though tend to be remembered (and appreciated) by larger segments of the Jewish population, frum and not-so-frum.

- Torah: 5 books of Moses. Sometimes erroneously called the "Jewish Bible", which in fact comprises all of the Goyish Old Testament. The Torah is made up of Genesis through Deuteronomy, though of course Jews don't call them that, although Deuteronomy is potentially one of the cooler Jewish names (beats Yekutiel any day).

- Tzaddik (Zaddik): Righteous person. Often used honorifically in reference to a great rabbinical personality (or anyone who the speaker determines to be such).

Also see here and here and here.