What is defined as taking a vehicle in the possession of another against his/her will?

The term that describes taking a vehicle in the possession of another against their will is specifically "carjacking." Carjacking involves forcibly stealing a vehicle from an individual who is either present inside the vehicle or in close proximity. It is characterized not just by the theft of the vehicle, but also by the element of force or intimidation used against the victim at the time of the act.

In contrast, robbery generally involves taking any property from a person through force or intimidation but does not specifically refer to vehicles. Theft, more broadly, involves taking someone else's property with the intent to permanently deprive them of it, but again, it does not capture the specific context of taking a vehicle from a person. Burglary involves unlawfully entering a building or structure to commit an offense, usually theft, but does not pertain to vehicles at all. Therefore, "carjacking" accurately captures the nature of the act as defined in the question.