The Collaborative International Dictionary of English v.0.48:

Isometric \I`so*met"ric\, Isometrical \I`so*met"ric*al\, a.
   [Iso- + Gr. me`tron measure.]
   1. Pertaining to, or characterized by, equality of measure.
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   2. (Crystallog.) Noting, or conforming to, that system of
      crystallization in which the three axes are of equal
      length and at right angles to each other; monometric;
      regular; cubic. Cf. Crystallization.
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   3. Of or pertaining to isometrics.
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   Isometric lines (Thermodynamics), lines representing in a
      diagram the relations of pressure and temperature in a
      gas, when the volume remains constant.

   Isometrical perspective. See under Perspective.

   Isometrical projection, a species of orthographic
      projection, in which but a single plane of projection is
      used. It is so named from the fact that the projections of
      three equal lines, parallel respectively to three
      rectangular axes, are equal to one another. This kind of
      projection is principally used in delineating buildings or
      machinery, in which the principal lines are parallel to
      three rectangular axes, and the principal planes are
      parallel to three rectangular planes passing through the
      three axes.
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The Collaborative International Dictionary of English v.0.48:

Perspective \Per*spec"tive\, n. [F. perspective, fr. perspectif:
   cf. It. perspettiva. See Perspective, a.]
   1. A glass through which objects are viewed. [Obs.] "Not a
      perspective, but a mirror." --Sir T. Browne.
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   2. That which is seen through an opening; a view; a vista.
      "The perspective of life." --Goldsmith.
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   3. The effect of distance upon the appearance of objects, by
      means of which the eye recognizes them as being at a more
      or less measurable distance. Hence, a["e]rial perspective,
      the assumed greater vagueness or uncertainty of outline in
      distant objects.
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            A["e]rial perspective is the expression of space by
            any means whatsoever, sharpness of edge, vividness
            of color, etc.                        --Ruskin.
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   4. The art and the science of so delineating objects that
      they shall seem to grow smaller as they recede from the
      eye; -- called also linear perspective.
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   5. A drawing in linear perspective.
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   Isometrical perspective, an inaccurate term for a
      mechanical way of representing objects in the direction of
      the diagonal of a cube.

   Perspective glass, a telescope which shows objects in the
      right position.
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