means A meeting at which people attempt to communicate with the spirits of the dead, usually guided by a medium.

from Straight from French séance, meaning 'a sitting' or 'session,' from the verb seoir, 'to sit' — itself descended from Latin sedēre, 'to sit' (the same root that gives us 'sediment' and 'sedentary'). In French it simply meant any formal sitting or meeting; English borrowed it in the 19th century and, as spiritualism swept the parlors, narrowed it to the particular sort of sitting where everyone holds hands in the dark and waits for the table to knock back.