Although I disagree with pg's usage of 'hater'(it's arrogantly dismissive in this context) I thought I would provide the surprisingly poignant urbandictionary.com definition:

" A person that simply cannot be happy for another person's success. So rather than be happy they make a point of exposing a flaw in that person.

Hating, the result of being a hater, is not exactly jealousy. The hater doesnt really want to be the person he or she hates, rather the hater wants to knock somelse down a notch."