From VG247: “Hearthstones next expansion is out now, and the new set is thematically built around the popular troll tribe thats also been a big part of WOWs recent Battle for Azeroth expansion.
As well as introducing a meaty chunk of new cards to the game, Rastakhans Rumble will also introduce a new keyword called Overkill. This rewards you for doing more damage to a minion than is required to kill it, and will, for example, allow you to take a second swing of a weapon.”
Source: N4G PC Hearthstone: Rastakhan's Rumble guide: keyword, Legendary and Spirit cards, Rumble Run