Plane \Plane\, n. [F. plane, L. plana. See Plane, v. & a.]
   1. (Geom.) A surface, real or imaginary, in which, if any two
      points are taken, the straight line which joins them lies
      wholly in that surface; or a surface, any section of which
      by a like surface is a straight line; a surface without
      curvature.
      [1913 Webster]

   2. (Astron.) An ideal surface, conceived as coinciding with,
      or containing, some designated astronomical line, circle,
      or other curve; as, the plane of an orbit; the plane of
      the ecliptic, or of the equator.
      [1913 Webster]

   3. (Mech.) A block or plate having a perfectly flat surface,
      used as a standard of flatness; a surface plate.
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   4. (Joinery) A tool for smoothing boards or other surfaces of
      wood, for forming moldings, etc. It consists of a
      smooth-soled stock, usually of wood, from the under side
      or face of which projects slightly the steel cutting edge
      of a chisel, called the iron, which inclines backward,
      with an apperture in front for the escape of shavings; as,
      the jack plane; the smoothing plane; the molding plane,
      etc.
      [1913 Webster]

   Objective plane (Surv.), the horizontal plane upon which
      the object which is to be delineated, or whose place is to
      be determined, is supposed to stand.

   Perspective plane. See Perspective.

   Plane at infinity (Geom.), a plane in which points
      infinitely distant are conceived as situated.

   Plane iron, the cutting chisel of a joiner's plane.

   Plane of polarization. (Opt.) See Polarization.

   Plane of projection.
      (a) The plane on which the projection is made,
          corresponding to the perspective plane in perspective;
          -- called also principal plane.
      (b) (Descriptive Geom.) One of the planes to which points
          are referred for the purpose of determining their
          relative position in space.

   Plane of refraction or Plane of reflection (Opt.), the
      plane in which lie both the incident ray and the refracted
      or reflected ray.
      [1913 Webster]