Honorable Kill

From wow.incgamers.com

Honorable Kill (HK)

An Honorable Kill is gained when you kill, or help to kill a player of the opposing faction of a similar level. The kill only counts if the target is in your level range, which varies but has the same limits as the experience point system. A HK give players Honor Points which are used when getting PvP Rewards. A Honorable Kill does not need to be performed honourably. Honorable Kills can be accumulated in 3 ways:

• Killing, or help to kill a player of opposing faction "Honorably" (at most 8 lvls lower at lvl 70).
• Being in the same party/raid, and be near someone killing an opponent honorably.
• Healing someone killing an opponent honorably.