(French). A spout or jet of water thrown up into the air, generally from an artificial fountain. The great jet at Versailles rises to a height of 100 feet; that at Chatsworth, the highest in existence, to 267 feet.
(French, from the Latin jactus, thrown; jaciv, to throw.)
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894