Maneuverable reentry vehicle
The maneuverable reentry vehicle (abbreviated MARV or MaRV) is a type of warhead for ballistic missiles that is capable of maneuvering and changing its trajectory. There are two general reasons to use MARV. One is to make it more difficult to track the re-entry vehicle (RV) and thereby make it more difficult to attack as it approaches its target.
Source: Wikipedia — Maneuverable reentry vehicle (CC BY-SA 4.0)