The Collaborative International Dictionary of English v.0.48:

Sault \Sault\, n. [OF., F. saut, fr. L. saltus. See Salt a
   leap.]
   A rapid in some rivers; as, the Sault Ste. Marie. [U.S.]
   --Bartlett.
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

18 Moby Thesaurus words for "sault":
   Niagara, cascade, cataract, chute, fall, falls, force, linn, nappe,
   rapid, rapids, riff, riffle, ripple, shoot, spout, waterfall,
   watershoot