Source : Webster's Revised Unabridged Dictionary (1913)

Visor \Vis"or\, n. [OE. visere, F. visi[`e]re, fr. OF. vis. See
   {Visage}, {Vision}.] [Written also {visar}, {visard},
   {vizard}, and {vizor}.]
   1. A part of a helmet, arranged so as to lift or open, and so
      show the face. The openings for seeing and breathing are
      generally in it.

   2. A mask used to disfigure or disguise. ``My very visor
      began to assume life.'' --Shak.

            My weaker government since, makes you pull off the
            visor.                                --Sir P.
                                                  Sidney.

   3. The fore piece of a cap, projecting over, and protecting
      the eyes.

Source : WordNet®

visor
     n 1: a piece of armor plate (with eye slits) fixed or hinged to a
          medieval helmet to protect the face [syn: {vizor}]
     2: a brim that projects to the front to shade the eyes; "he
        pulled down the bill of his cap and trudged ahead" [syn: {bill},
         {peak}, {eyeshade}, {vizor}]