1. The valley of Hinnom, near Jerusalem, where propitiatory sacrifices were made to Moloch. [II Kings 23:10];
2. Hell;
3. Any place of extreme torment or suffering.
http://dictionary.reference.com/browse/gehenna
Gehenna (also gehenom or gehinom) is the Jewish equivalant to the Christian Purgatory. The name derived from the burning garbage dump near Jerusalem (the Valley of Hinnom), metaphorically identified with the entrance to the underworld. Gehenna is cited in the New Testament and in early Christian writing to represent the place where evil will be destroyed. It lends its name to Islam's hell, Jahannam. In both Rabbinical Jewish and Christian writing, Gehenna as a destination of the wicked is different from Sheol, the abode of all the dead.
http://en.wikipedia.org/wiki/Valley_of_Hinnom
