The Collaborative International Dictionary of English v.0.48:

Exterior \Ex*te"ri*or\, a. [L. exterior, compar. of exter or
   exterus on the outside, outward, foreign, strange, a compar.
   fr. ex: cf. F. ext['e]rieur. See Ex-, and cf. Extreme,
   Interior.]
   1. External; outward; pertaining to that which is external;
      -- opposed to interior; as, the exterior part of a
      sphere.
      [1913 Webster]

            Sith nor the exterior nor the inward man
            Resemble that it was.                 --Shak.
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   2. External; on the outside; without the limits of;
      extrinsic; as, an object exterior to a man, opposed to
      what is within, or in his mind.
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            Without exterior help sustained.      --Milton.
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   3. Relating to foreign nations; foreign; as, the exterior
      relations of a state or kingdom.
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   Exterior angle (Geom.), the angle included between any side
      of a triangle or polygon and the prolongation of the
      adjacent side; also, an angle included between a line
      crossing two parallel lines and either of the latter on
      the outside.

   Exterior side (Fort.), the side of the polygon upon which a
      front of fortification is formed. --Wilhelm.
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   Note: See Illust. of Ravelin.
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The Collaborative International Dictionary of English v.0.48:

Exterior \Ex*te"ri*or\, n.
   1. The outward surface or part of a thing; that which is
      external; outside.
      [1913 Webster]

   2. Outward or external deportment, form, or ceremony; visible
      act; as, the exteriors of religion.
      [1913 Webster]

WordNet (r) 3.0 (2006):

exterior
    adj 1: situated in or suitable for the outdoors or outside of a
           building; "an exterior scene"; "exterior grade plywood";
           "exterior paints" [ant: interior]
    n 1: the region that is outside of something [syn: outside,
         exterior] [ant: inside, interior]
    2: the outer side or surface of something [syn: outside,
       exterior] [ant: inside, interior]

Moby Thesaurus II by Grady Ward, 1.0:

91 Moby Thesaurus words for "exterior":
   airscape, alien, apparent, apparent character, appearances, border,
   circumference, cityscape, cloudscape, coating, cortex, cortical,
   covering, crust, diorama, display, envelope, epidermic, epidermis,
   exomorphic, exotic, exteriors, external, external appearance,
   externals, extraneous, extrinsic, facade, face, facet, facing,
   farmscape, foreign, fringe, front, gaudiness, integument, interior,
   landscape, lineaments, mere externals, meretriciousness, open,
   ostent, out, outer, outer face, outer layer, outer side,
   outer skin, outermost, outline, outlying, outmost, outside,
   outstanding, outward, outward appearance, outward show,
   outward-facing, pastoral, peripheral, periphery, public,
   public image, rind, riverscape, roundabout, scape, scene, seapiece,
   seascape, seeming, shell, show, skin, skyscape, snowscape,
   speciousness, superficial, superficiality, superficies,
   superstratum, surface, surface appearance, surface show, top,
   townscape, vain show, view, waterscape