Source : Webster's Revised Unabridged Dictionary (1913)

Sunbonnet \Sun"bon"net\, n.
   A bonnet, generally made of some thin or light fabric,
   projecting beyond the face, and commonly having a cape, --
   worn by women as a protection against the sun.

Source : WordNet®

sunbonnet
     n : a large bonnet that shades the face; worn by girls and women
         [syn: {sunhat}]