The Collaborative International Dictionary of English v.0.48:

Sliding \Slid"ing\, a.
   1. That slides or slips; gliding; moving smoothly.
      [1913 Webster]

   2. Slippery; elusory. [Obs.]
      [1913 Webster]

            That sliding science hath me made so bare.
                                                  --Chaucer.
      [1913 Webster]

   Sliding friction (Mech.), the resistance one body meets
      with in sliding along the surface of another, as
      distinguished from rolling friction.

   Sliding gunter (Naut.), a topmast arranged with metallic
      fittings so as to be hoisted and lowered by means of
      halyards.

   Sliding keel (Naut), a movable keel, similar to a
      centeboard.

   Sliding pair. (Mech.) See the Note under Pair, n., 7.

   Sliding rule. Same as Slide rule, under Slide, n.

   Sliding scale.
      (a) A scale for raising or lowering imposts in proportion
          to the fall or rise of prices.
      (b) A variable scale of wages or of prices.
      (c) A slide rule.

   Sliding ways (Naut.), the timber guides used in launching a
      vessel.
      [1913 Webster]

WordNet (r) 3.0 (2006):

sliding keel
    n 1: a retractable fin keel used on sailboats to prevent
         drifting to leeward [syn: centerboard, centreboard,
         drop keel, sliding keel]