Source : Webster's Revised Unabridged Dictionary (1913)

Duffer \Duf"fer\, n.
   1. (Mining) See {Shicer}.

   2. (Zo["o]l.) Any common domestic pigeon.

Duffer \Duf"fer\, n.
   One who duffs cattle, etc. [Australia]

         Unluckily, cattle stealers are by no means so rare as
         would be desirable; they are locally known as duffers.
                                                  --Baden-Powell.

Duffer \Duf"fer\, n.
   1. A peddler or hawker, especially of cheap, flashy articles,
      as sham jewelry; hence, a sham or cheat. [Slang, Eng.]
      --Halliwell.

   2. A stupid, awkward, inefficient person.[Slang]

Source : WordNet®

duffer
     n : an incompetent or clumsy person; "as a golfer he was only a
         duffer"