The final day of the festival of Sukkot, on which the annual cycle of the reading of the Torah reaches its completion, and a new cycle is begun with the start of Genesis.
The start of the new cycle is traditionally marked by the carrying of the Torah scrolls in procession round the synagogue to the accompaniment of dancing and singing.
Simchat Torah/ˌsɪmxət ˈtɔːrə/ /ˌsɪmkət ˈtɔːrə/ /ˌsɪmxət ˈtəʊrə/
Mid 18th century. From post-biblical Hebrew śimḥaṯ tōrāh from śimḥaṯ, construct state of śimḥāh act of rejoicing + tōrāh.