1. An expression of complete indifference to the target's opinions.
2. A pathetic attempt at a witty comeback, most commonly used by Deviantart/Youtube users who are unable to stand criticism.
Originally, this term was used sparingly, and only when it truly stung, much like "That's what she said". However, like "That's what she said", it has been spammed so far into the ground by the aforementioned "artists" that it's simply pathetic.
1. Someone overhears a jealous douchebag talking down on them, responds with an over-the-shoulder "Haters gonna hate", which shatters the trash-talker's massive ego.
2. Someone posts a mildly critical comment on a hypersensitive Youtube user's video, to which the user replies "FUCK U HATERS GONNA HATE FAG BLOCKED LOL"