Kabbalah- literally, "that which is passed down." Refers to the field of Jewish Mysticism. Also a really cool Jewish Rock Band.
Kabbalat Panim - the first part of a traditional Jewish wedding, when bride and groom greet and entertain their guests
Kallah - bride
Kaddish- special prayer, often said by those in mourning. Requires a quorum (minyan) of 10 men to recite.
Kashrut- the concept that food must be kosher (ok for Jews to eat)
Kavannah - sincerity and fervor while praying
Kavod - honor
Kedusha- the holiest part of the prayer service, where everyone must be silent and not move. Also means holiness
Kesher - an emotional connection between two people
Kiddush- sanctification of the meal over wine. Also refers to a nice spread after shul is over.
Kiddush Hashem- sanctification of the name of G-d. Opposite of chillul Hashem. Something that brings honor to the Jewish People.
Kinneret – the body of water in Israel
Kippah Sruga- crocheted skullcap
Klezmer – a type of jewish music emanating from eastern Europe. e.g. Andy Statman
kol b'seder - everything's cool; etymological origin of the term "copacetic"
Kol Isha- the voice of a woman (usually singing), which men are prohibited from listening to
Kollel- place where married men sit and learn Torah all day
Kotel - the Western Wall
K'tiva v'katima tova – You should be written and inscribed for good, a new year’s greeting
Kugel - noodle or potato casserole; can be sweet or savory
Kumzitz- singalong with story telling
Kvetch - (verb) to complain; (noun) a complaining person