The Collaborative International Dictionary of English v.0.48:

Jet d'eau \Jet` d'eau"\; pl. Jets d'eau. [F., a throw of
   water. See Jet a shooting forth.]
   A stream of water spouting, esp. upward, from a fountain or
   pipe for ornament; also, the fountain or pipe from which it
   issues.
   [Webster 1913 Suppl.]