H8r

H8r is a kewl way to write "hater." It's one example of leetspeak, which is slang that uses numbers and symbols to replace letters. For that reason, you're most likely to encounter h8r in chat and forum messages, sent by users who are familiar with (and commonly use) leetspeak.

Haters, of course, are people who are angry at or jealous of other people. These negative emotions cause haters to "hate on" their targets - issuing vicious insults and critiques, and generally doing whatever they can to make their targets' lives worse.