n. then v. Based on the model of the noun "hard on", a hate on is an active hatred for someone or something that causes a visible physical reaction in a similar fashion that an erection would be a tell-tale sign of affection. Despite its origin, it is rarely used in a sexual context. It is male juvenile slang in the sense that it links, even indirectly, an emotion (hatred, jealousy, envy) to the male teenage obsession with the penis.

v. To be jealous of another's success or talent. Note that the person being hated on must posess these qualties; thus it is not possible to hate on Ja Rule,Hilary Duff, or Paris Hilton, for example.

to insult or verbally attack someone. originally implied jelousy, now also used for more generally applied abuse.