The Collaborative International Dictionary of English v.0.48:

Slide \Slide\, n. [AS. sl[imac]de.]
   1. The act of sliding; as, a slide on the ice.
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   2. Smooth, even passage or progress.
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            A better slide into their business.   --Bacon.
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   3. That on which anything moves by sliding. Specifically:
      (a) An inclined plane on which heavy bodies slide by the
          force of gravity, esp. one constructed on a mountain
          side for conveying logs by sliding them down.
      (b) A surface of ice or snow on which children slide for
          amusement.
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   4. That which operates by sliding. Specifically:
      (a) A cover which opens or closes an aperture by sliding
          over it.
      (b) (Mach.) A moving piece which is guided by a part or
          parts along which it slides.
      (c) A clasp or brooch for a belt, or the like.
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   5. A plate or slip of glass on which is a picture or
      delineation to be exhibited by means of a magic lantern,
      stereopticon, or the like; a plate on which is an object
      to be examined with a microscope.
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   6. The descent of a mass of earth, rock, or snow down a hill
      or mountain side; as, a land slide, or a snow slide; also,
      the track of bare rock left by a land slide.
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   7. (Geol.) A small dislocation in beds of rock along a line
      of fissure. --Dana.
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   8. (Mus.)
      (a) A grace consisting of two or more small notes moving
          by conjoint degrees, and leading to a principal note
          either above or below.
      (b) An apparatus in the trumpet and trombone by which the
          sounding tube is lengthened and shortened so as to
          produce the tones between the fundamental and its
          harmonics.
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   9. (Phonetics) A sound which, by a gradual change in the
      position of the vocal organs, passes imperceptibly into
      another sound.
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   10. (Steam Engine)
       (a) Same as Guide bar, under Guide.
       (b) A slide valve.
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   Slide box (Steam Engine), a steam chest. See under Steam.


   Slide lathe, an engine lathe. See under Lathe.

   Slide rail, a transfer table. See under Transfer.

   Slide rest (Turning lathes), a contrivance for holding,
      moving, and guiding, the cutting tool, made to slide on
      ways or guides by screws or otherwise, and having compound
      motion.

   Slide rule, a mathematical instrument consisting of two
      parts, one of which slides upon the other, for the
      mechanical performance of addition and subtraction, and,
      by means of logarithmic scales, of multiplication and
      division.

   Slide valve.
       (a) Any valve which opens and closes a passageway by
           sliding over a port.
       (b) A particular kind of sliding valve, often used in
           steam engines for admitting steam to the piston and
           releasing it, alternately, having a cuplike cavity in
           its face, through which the exhaust steam passes. It
           is situated in the steam chest, and moved by the
           valve gear. It is sometimes called a D valve, -- a
           name which is also applied to a semicylindrical pipe
           used as a sliding valve.
           [1913 Webster] In the illustration, a is the cylinder
           of a steam engine, in which plays the piston p; b the
           steam chest, receiving its supply from the pipe i,
           and containing the slide valve s, which is shown as
           admitting steam to one end of the cylinder through
           the port e, and opening communication between the
           exhaust passage f and the port c, for the release of
           steam from the opposite end of the cylinder.
           [1913 Webster]

WordNet (r) 3.0 (2006):

slide valve
    n 1: valve that opens and closes a passageway by sliding over a
         port