The Collaborative International Dictionary of English v.0.48:

Rapid \Rap"id\, Rapids \Rap"ids\(r[a^]p"[i^]dz), n. [Cf. F.
   rapide. See Rapid, a.]
   The part of a river where the current moves with great
   swiftness, but without actual waterfall or cascade; sometimes
   called whitewater; -- usually used in the plural; as, the
   Lachine rapids in the St. Lawrence. For boaters on the river,
   it is a place that can be hazardous, with danger of capsizing
   or crashing into large rocks.
   [1913 Webster +PJC]

         Row, brothers, row, the stream runs fast,
         The rapids are near, and the daylight's past. --Moore.
   [1913 Webster] Rapid-fire

Moby Thesaurus II by Grady Ward, 1.0:

59 Moby Thesaurus words for "rapids":
   belch, burst, cascade, cataract, chute, collapse, comedown, crash,
   debacle, debouchment, declension, declination, defluxion,
   descending, descension, descent, dissiliency, down, downbend,
   downcome, downcurve, downfall, downflow, downgrade, downpour,
   downrush, downtrend, downturn, downward trend, drop, dropping,
   eructation, eruption, fall, falling, flare-up, gravitation, gush,
   inclination, jet, outbreak, outburst, plummeting, pounce, rapid,
   riff, riffle, ripple, rush, sault, shoot, spate, spew, spurt,
   stoop, swoop, torrent, volcan, waterfall



U.S. Gazetteer Places (2000):

Rapids, NY -- U.S. Census Designated Place in New York
   Population (2000):    1356
   Housing Units (2000): 582
   Land area (2000):     3.666546 sq. miles (9.496311 sq. km)
   Water area (2000):    0.000000 sq. miles (0.000000 sq. km)
   Total area (2000):    3.666546 sq. miles (9.496311 sq. km)
   FIPS code:            60609
   Located within:       New York (NY), FIPS 36
   Location:             43.101324 N, 78.641134 W
   ZIP Codes (1990):
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Rapids, NY
    Rapids