From Halopedia, the Halo wiki
Splatter Spree is a spree medal awarded in Halo 3, Halo 3: ODST, Halo: Reach and Halo: Spartan Assault and Halo: Spartan Strike multiplayer, campaign and Firefight. In Halo: 3 and Halo 3: ODST it is awarded for killing five opponents in a row with a splatter without dying. In Halo: Reach the medal does not require kills to be consecutive, just that the player kill five enemies with splatters without dying. In Spartan Assault and Spartan Strike it is awarded for killing three enemies in a row with a vehicle, without being hit.
In Halo 3 and Halo 3: ODST it is represented by a steel four-pointed star with a blue-rimmed tire in the center of the medal. In Halo: Reach it is represented by a steel four-pointed star with the Splatter Kill Medal symbol in the center, with a blue blood splatter rather than red. In Spartan Assault and Spartan Strike it is represented by a shield with a single chevron and a steering wheel.