The Collaborative International Dictionary of English v.0.48:

Greenhead \Green"head`\, n. (Zool.)
   (a) The mallard.
   (b) The striped bass. See Bass. Greenhead

The Collaborative International Dictionary of English v.0.48:

Greenhead \Green"head\, Greenhood \Green"hood\, n.
   A state of greenness; verdancy. --Chaucer.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Mallard \Mal"lard\, n. [F. malari,fr. m[^a]le male + -art =
   -ard. See Male, a., and -ard.]
   1. (Zool.) A drake; the male of Anas boschas.
      [1913 Webster]

   2. (Zool.) A large wild duck (Anas boschas) inhabiting both
      America and Europe. The domestic duck has descended from
      this species. Called also greenhead.
      [1913 Webster]