The opposite of a hardcore scream. A hardcore growl is a low, rumbling sound in the throat. It works better with grindcore or emo-core style music. Not so much on the level of regular screamo. For example: You couldn't growl to a Rise Against song. However, the screaming done my Alesana works well because they're more hardcore.
Dude, Denny Diablo from Alesana is amazing at hardcore growling