Source : Webster's Revised Unabridged Dictionary (1913)

Sunglass \Sun"glass`\, n.; pl. {Sunglasses}.
   A convex lens of glass for producing heat by converging the
   sun's rays into a focus. ``Lighting a cigar with a
   sunglass.'' --Hawthorne.

Source : WordNet®

sunglasses
     n : spectacles that are darkened or polarized to protect the
         eyes from the glare of the sun; "he was wearing a pair of
         mirrored shades" [syn: {dark glasses}, {shades}]