The following sites have Yiddish dictionaries¹

Harkavy Yiddish Dictionary   Yiddish Dictionary online    Jastrow Talmud Dictionary   Google Translate   Yiddish-Hebrew Dictionary    Yiddish words in Likkutei Sichos

A .  B .  C .  D .  E .  F .  G .  H .  I .   J .   K .   L .  M .  N .  O .  P .  Q .  R .  S .  T .  U .  V .  W .  X .  Y .  Z . 

Adam Kadmon: Primordial Man

Abba (Father): Abba is the general partzuf of chochmah ("wisdom"), the first conscious power in the soul.

Abraham: The first Jew and first of the three Patriarchs Abraham, Isaac, and Jacob.

Acharon shel Pesach: The Last Day of Pesach.

Acharonim: Halachic authorities of the period since the publication of the Shulchan Aruch in the sixteenth century. Adam Kadmon is the first partzuf.

Adar: the twelfth of the twelve months of the Jewish calendar.

Admor: Hebrew initials for Adonenu Morenu VeRabenu (Our master, Our teacher our Rabbi). This is a title commonly used with Chassidic Rebbes. 

Adnut: Adnut is a Holy Name of G-d.

Afula: A town in north-central Israel.

Aggados; aggad'ta: Non-legal teachings on the non-literal level of interpretation known as derush.

Ahavah ("love"): A spiritual state associated with the sefirah of chesed.

Ahavas HaShem: Loving G-d.

Ahavas HaTorah: Loving the Torah.

Ahavas Yisrael: Loving a fellow Jew.

Akeida: lit. 'binding' Refers to the binding of Yitzchok on the alter.

Akudim: ("bound," "striped") the first stage in the development of the world of Atzilut.

Akvah: Akvah is a Holy Name of G-d.

Al Kiddish HaShem: Heb. for the sanctification of HaShem. refers to someone who is killed for being a Jew.

Al-bam: Al-bam is a method of alphabetic transformation.

Alef: the 1st letter of the Hebrew alphabet.

Alef-beit: The Hebrew Alphabet consists of twenty-two letters

Aliyah: (pl., aliyos; lit., "ascent") the honor of being called upon for the public Reading of the Torah

Alma d'isgalya: the world of revelation'; (Aramaic) The spiritual realm in which Divinity is revealed.

Alma d'iskasya: the world of concealment'; (Aramaic) The spiritual realm in which Divinity is concealed.

Alsheich: Jewish Biblical commentator Rabbi Moshe Al Sheich

Alter Rebbe: Rabbi Shneur Zalman of Liadi of blessed memory, the first Rebbe of the Chabad Chassidic movement, also known as the Baal HaTanya, the author of the Tanya

Am HaAretz: 'people of the land' and refers to those who are ignorant of the Torah.

Amidah: (The "Standing" prayer) The center core and highest point of every prayer service.

Amora(Amoraim): Rabbis of the post Mishnahaic period. 

Amorah: Biblical city filled with wicked people

Anash: Lit., “the people with whom we are at peace”; this term is used to refer to other members of one’s Chassidic community

Anavah: ("humility") Unpretensciousness; the third of the four stages in the nullification of the ego

Apikores: Heretic pl. Apikorsim

Aramaic: The language in which the Talmud is written.

Ari or Arizal: Rabbi Isaac Luria 1534-1572, whose teachings form the core of Kabbalistic doctrine and the basis for understanding the Zohar. Hebrew initials of the words Adoni Rabbenu Yitzchok

Arich Anpin: ("The Long Face" or "The Infinitely Patient One") Arich Anpin is the external partzuf of keter.

Arvit: The evening prayer, also known as Maariv, established by Yaakov Avinu

Ashrei: A prayer recited three times a day, consisting of Psalm 145 preceded by two other verses beginning with the word Ashrei and one additional concluding verse.

Ashuritic script: The sacred Hebrew script used in the ritual writing of Torah scrolls as well as Tefilin and mezuzah parchments.

Asiyah: (Olam Ha'Asiyah The World of Actionlowest of the four worlds of Creation. 2. Making' the lowest of the Four Worlds.

At-bach: a method of alphabetic transformation.

At-bash: a method of alphabetic transformation.

Atik Yomin: ("The Ancient of Days") Atik Yomin is the inner partzuf of keter,

Atika Kadisha: ("The Holy Ancient of One" Aramaic) a synonym for Atik Yomin; or keter in general.

Atzilut: ("Emanation") Atzilut is the first and highest of the four worlds of Creation.

Atzmut: (G-d's Absolute Essence)

Av: The fifth of the twelve months of the Jewish calendar.

Avodah: lit.,:work' or:service'. Divine service, (in Torah usage) particularly through prayer and (in Chassidic usage) through the labor of self-refinement.

Avodas HaTefillah: lit. “the service of prayer,” prayer at length accompanied by lengthy meditation on Chassidic concepts

Avraham Aveinu: Our father Abraham

Ayin:(Hebrew letter) the 16th letter of the Hebrew alphabet.

Ayin: Nothingness, spirituality from the perpective of physicality. See Yesh

 

1) There is a Sichos dictionary by Zalman Goldstein.