Megillah is an ancient Hebrew word which is best translated as "Scroll" (as in a scroll of parchment). It is used to refer to five books in the "Writings" (Ketubim) section of The Tanakh (the complete Old Testament according to the Jewish tradition).
The five Megillot (the plural) are as follows.
- Shir HaShirim - The Song of Songs. Written by King Solomon in the form of a love story, as a representation of the relationship between G-D and the Jewish people. It is read on Pesach. Some Synagogues read it every Friday afternoon before Shabbat.
- Ruth. This is the story of a servant girl who converted to the Jewish religion of her friend Naomi. "Wherever you go, I will go and whatever you do, I will do. Your people will be my people, and your G-D will be my G-D". It is read on Shavuot.
- Eichah - Lamentations. Written by the prophet Jeremiah, it describes his feelings on the destruction of the Temple in Jerusalem. It is read on Tisha B'Av, the Jewish fast day which commemorates the destruction of the Temple.
- Kochelet - Ecclesiastes. A somewhat philosopical work also by King Solomon. Contains the famous passage "A time to be born, and a time to die...". Read on Succot.
- Esther. Also known as "The Megillah" as it is the most well known. Talks about a young girl - Esther - who becomes the wife of the king to save the Jewish People from the tyrant Haman. Read on Purim. The only book in the Old Testament not to mention G-D directly. This is why there is a tradition to wear fancy dress on Purim - G-D's work can be seen, but he was masked.
The term is also used as a slang word for an (often unnecessarily long) story about something. "He was going on and on, giving me the whole megillah, before he got to the point".