The Collaborative International Dictionary of English v.0.48:

Curtail dog \Cur"tail dog`\ (d[o^]g`; 115).
   A dog with a docked tail; formerly, the dog of a person not
   qualified to course, which, by the forest laws, must have its
   tail cut short, partly as a mark, and partly from a notion
   that the tail is necessary to a dog in running; hence, a dog
   not fit for sporting.
   [1913 Webster]

         Hope is a curtail dog in some affairs.   --Shak.
   [1913 Webster]