Source : Webster's Revised Unabridged Dictionary (1913)

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

   2. Slippery; elusory. [Obs.]

            That sliding science hath me made so bare.
                                                  --Chaucer.

   {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.

Source : WordNet®

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