Whirling Lunge is a feature granted to members of the Barbarian class that choose the Whirling Slayer Feral Might option.
Whirling Lunge
Barbarian feature
Trigger: your attack reduces an enemy to 0 hit points
Effect: "You shift 2 squares and then deal 1[W] damage (off-hand weapon) to an enemy adjacent to you that you can see." [PrP:10]
Striking down one foe, you whirl deeper into enemy ranks.