Source : Webster's Revised Unabridged Dictionary (1913)

Jinx \Jinx\, n.
   A person, object, influence, or supernatural being which is
   supposed to bring bad luck or to cause things to go wrong.
   [Slang]

Source : WordNet®

jinx
     n 1: a person believed to bring bad luck to those around him
          [syn: {jonah}]
     2: an evil spell; "a witch put a curse on his whole family";
        "he put the whammy on me" [syn: {hex}, {curse}, {whammy}]
     v 1: cast a spell over someone or something; put a hex on someone
          or something [syn: {hex}, {bewitch}, {glamour}, {witch},
           {enchant}]
     2: foredoom to failure; "This project is jinxed!"