- Lachen mit yash-tsherkes - Forced or false laugh; laugh with anguish
- Laidik-gaier - Idler, loafer
- Lamden - Scholar, erudite person, learned man
- Lang leben zolt ir! - Long may you live!
- Lantsman - Countryman, neighbour, fellow townsman from "old country."
- Lapeh - Big hand
- (A) Lebedikeh velt! - A lively world!
- (A) Lebediker - Lively person
- (A) Leben ahf dein kop! - Words of praise like; Well said! Well done! (Lit., A long life upon your head.)
- Lebst a chazerishen tog! - Living high off the hog! Newly rich life.
- L'chei-im, le'chayim! - To life! (the traditional Jewish toast); To your health, skol
- Leibtzudekel - Sleeveless shirt (like bib) with fringes, worn by orthodox Jews
- Leiden - To suffer
- Lemeshkeh - Milquetoast, bungler
- Leveiyeh - Funeral
- Lig in drerd! - Get lost! Drop dead! (Lit., Bury yourself!)
- Ligner - Liar
- Litvak - Lithuanian; Often used to connote shrewdness and skepticism, because the Lithuanian Jews are inclined to doubt the magic powers of the Hasidic leaders; Also, a person who speaks with the Northeastern Yiddish accent.
- Loch - Hole
- Loch in kop - Hole in the head.
- Lokshen - Noodles, but often meaning 'nonsense' or bullshit
- Loz mich tzu ru! - Leave me alone! (Lit., Let me be in peace!)
- Luftmentsh - Person who has no business, trade, calling, nor income.
- Luch in kup - A hole in the head ( " I need this like a luch in kup").