Ouija board
Concise Oxford English Dictionary © 2008 Oxford University Press:
Ouija board /ˈwiːdʒə/
▶noun trademark a board with letters, numbers, and other signs around its edge, to which a planchette or other pointer moves, supposedly in answer to questions from people at a seance.
– origin C19: Ouija from Fr. oui ‘yes’ + Ger. ja ‘yes’.
'Ouija board' also found in these Oxford entries:

