[1] : The Collaborative International Dictionary of English v.0.48

fresnel lens \fres`nel" lens"\ see fresnel lamp. optics
   see under lens.
   1913 webster
see also:
fresnel lamp lens 

[2] : The Collaborative International Dictionary of English v.0.48

lens \lens\ le^nz, n.; pl. lenses -e^z. l. lens a
   lentil. so named from the resemblance in shape of a double
   convex lens to the seed of a lentil. cf. lentil. opt.
   a piece of glass, or other transparent substance, ground with
   two opposite regular surfaces, either both curved, or one
   curved and the other plane, and commonly used, either singly
   or combined, in optical instruments, for changing the
   direction of rays of light, and thus magnifying objects, or
   otherwise modifying vision. in practice, the curved surfaces
   are usually spherical, though rarely cylindrical, or of some
   other figure.
   1913 webster lenses
   1913 webster

   note: of spherical lenses, there are six varieties, as shown
         in section in the figures herewith given: viz., a
         plano-concave; b double-concave; c plano-convex; d
         double-convex; e converging concavo-convex, or
         converging meniscus; f diverging concavo-convex, or
         diverging meniscus.
         1913 webster

   crossed lens opt., a double-convex lens with one radius
      equal to six times the other.

   crystalline lens. anat. see eye.

   fresnel lens opt., a compound lens formed by placing
      around a central convex lens rings of glass so curved as
      to have the same focus; used, especially in lighthouses,
      for concentrating light in a particular direction; -- so
      called from the inventor.

   multiplying lens or multiplying glass opt., a lens one
      side of which is plane and the other convex, but made up
      of a number of plane faces inclined to one another, each
      of which presents a separate image of the object viewed
      through it, so that the object is, as it were, multiplied.
      

   polyzonal lens. see polyzonal.
      1913 webster
see also:
lenses lentil crossed lens crystalline lens eye fresnel lens 
multiplying lens multiplying glass polyzonal lens polyzonal 

[3] : WordNet (r) 2.0

fresnel lens
     n : lens composed of a number of small lenses arranged to make a
         lightweight lens of large diameter and short focal length

Fresnel Lens >> F Words
Fresnel Lens, definition of term: Fresnel Lens
fresnel+lens_pag1.html

Lens >> L Words
Lens, definition of term: Lens
lens_pag1.html

Zoom Lens >> Z Words
Zoom Lens, definition of term: Zoom Lens
zoom+lens_pag1.html

Diverging Lens >> D Words
Diverging Lens, definition of term: Diverging Lens
diverging+lens_pag1.html

Convex Lens >> C Words
Convex Lens, definition of term: Convex Lens
convex+lens_pag1.html

Concave Lens >> C Words
Concave Lens, definition of term: Concave Lens
concave+lens_pag1.html

Contact Lens >> C Words
Contact Lens, definition of term: Contact Lens
contact+lens_pag1.html

Converging Lens >> C Words
Converging Lens, definition of term: Converging Lens
converging+lens_pag1.html

Camera Lens >> C Words
Camera Lens, definition of term: Camera Lens
camera+lens_pag1.html