Vehicle Kill
From Halopedia, the Halo wiki
Vehicle Kill is a medal awarded in Halo 4 multiplayer and Spartan Ops for killing an enemy with the a vehicle-mounted weapon. The player will also be awarded the medal if an AI passenger in a vehicle they are driving kills an enemy with the vehicle's turret. It is represented by an M247T Medium Machine Gun silhouette on a blue circle atop a grey four-pointed star.