The following sites have Yiddish dictionaries¹

Harkavy Yiddish Dictionary  Yiddish Dictionary online

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 . 

Ikvesa DiMeshicha; also Ikvos Meshicha; (Aramaic):the generation that can hear the approaching 'footsteps' of Mashiach.

Iluy:genius

Imma Ila'ah (the higher mother):Imma Ila'ah is the higher of the two primary partzufim which develop from the sefirah of binah.

In velt, oys velt ("In the world, outside the world"):In velt, oys velt is a Yiddish phrase conveying the Chassidic ideal of being grounded on the physical plane of reality while simultaneously maintaining a spiritual consciousness which transcends the confines of the material realm.

Inyan:A spiritual concept or idea. A general idea as opposed to

Isaiah:First of the three major prophets Isaiah, Jeremiah, Ezekiel. One of the 24 Books of the Bible. Isaiah is renowned for its message of consolation and hope and its vivid portrayal of the glory of the Messianic Era.

Ishapcha: אתהפכא - “turning over” — transforming one’s physical nature to holiness.

Iskafya (iskafia): אתכפיא - Self-restraint in order to subdue the animal soul

Israel:an additional name given the patriarch Jacob and, by extension, the entire Jewish People.

Itaruta d'letata: An awakening from below. This usually results in a commensurate response from Above (itaruta d'leila).

Itaruta d'leila: An awakening (inspiration) that is initiated from Above. This can come about in two ways: a) initiated by G-d, independent of any stimulus by the recipient(s), b) in response to the efforts of a recipient(s) to establish a more elevated and intimate relationship with G-d (Itaruta d'letata).

Israelite:a Jew who is neither a Kohen (priest) nor a Levi (Levite).

Iyar:Iyar is the second of the twelve months of the Jewish calendar.