The Collaborative International Dictionary of English v.0.48:

jinx \jinx\ (j[i^][ng]ks), n.
   A person, object, influence, or supernatural being which is
   supposed to bring bad luck or to cause things to go wrong.
   [Slang]
   [Webster 1913 Suppl.]

The Collaborative International Dictionary of English v.0.48:

jinx \jinx\ (j[i^][ng]ks), v. t.
   To bring bad luck to; to cause to malfunction or go wrong;
   as, some superstitious people are reluctant to predict
   success for fear it will jinx them. [Slang]
   [PJC]

WordNet (r) 3.0 (2006):

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

Moby Thesaurus II by Grady Ward, 1.0:

86 Moby Thesaurus words for "jinx":
   Jonah, abuse, afflict, aggrieve, bad influence, bedevil, befoul,
   bewitch, blight, bring bad luck, cantrip, charm, condemn, corrupt,
   crucify, curse, damage, damn, defile, demonize, deprave, despoil,
   destroy, diabolize, disadvantage, disserve, distress,
   do a mischief, do evil, do ill, do wrong, do wrong by, doom,
   enchantment, envenom, evil eye, evil genius, evil star, exorcism,
   get into trouble, glamour, harass, harm, hex, hoodoo, hurt,
   ill wind, impair, infect, injure, magic spell, malediction,
   malevolent influence, malocchio, maltreat, menace, mistreat,
   molest, nemesis, obsess, outrage, overlook, persecute,
   play havoc with, play hob with, poison, pollute, possess,
   prejudice, sabotage, savage, scathe, spell, taint, threaten,
   torment, torture, violate, voodoo, wanga, weird, whammy, witch,
   wound, wreak havoc on, wrong