Source : Webster's Revised Unabridged Dictionary (1913)

Hobnail \Hob"nail`\, n. [1st hob + nail.]
   1. A short, sharp-pointed, large-headed nail, -- used in
      shoeing houses and for studding the soles of heavy shoes.

   2. A clownish person; a rustic. --Milton.

   {Hobnail liver} (Med.), a disease in which the liver is
      shrunken, hard, and covered with projections like
      hobnails; one of the forms of cirrhosis of the liver.

Hobnail \Hob"nail`\, v. t.
   To tread down roughly, as with hobnailed shoes.

         Your rights and charters hobnailed into slush.
                                                  --Tennyson.

Source : WordNet®

hobnail
     n : a short nail with a thick head; used to protect the soles of
         boots
     v : supply with hobnails