Source : Webster's Revised Unabridged Dictionary (1913)

Fumbler \Fum"bler\, n.
   One who fumbles.

Source : WordNet®

fumbler
     n : someone who makes mistakes because of incompetence [syn: {bungler},
          {blunderer}, {bumbler}, {stumbler}, {sad sack}, {botcher},
          {butcher}, {fuckup}]