adon olam

a hymn in the traditional Jewish liturgy, usually recited before Shacharit and often sung after services in synagogue, made up of traits attributed to God

afikomen

a piece of matzah from the Passover seder traditionally hidden by adults, found by the children (or vice versa), and then ransomed for gifts after the meal. "The last piece of matzoh...eaten at the meal." (Steinmetz)

Akedah

The binding of Isaac (episode in the Torah)

al regel achat

lit. "on one foot"; off-the-cuff; "To answer a question or deal with a query very briefly and cursorily." (Glinert)

aliyah

immigration to Israel

"calling to the reading of the Torah" (Glinert)

ascent of the soul of a deceased person to a higher level, as is believed to happen on their yartzeit

ascent

am haaretz

Vulgar, boorish person

People of the land

Bumpkin, ignoramus, uneducated person

amen

Agreed. "The word used at the end of prayer to signify affirmation." (Rosten)

Amida

The Shemoneh Esrei prayer, which is said while standing [Amida, lit. "standing".]

apikoros

heretic, non-believer, especially one with great knowledge of Judaism

aron kodesh

"Literally, "holy ark"." (JPS)