“Panzer” in a very general protective sense translates to “Armour”. Brustpanzer -> Chest armour. Even a turtle’s shell is a Panzer. Typically a hard enclosure protecting the main body of a thing. But not its extremities. A “helmet” is a “Helm”. Though any element can be “gepanzert”, or “armoured”.

It is important to note that Panzer mostly refers to protection from violence. A civilian car is never “gepanzert”, neither is a padded skateboarder. Unless you’re mocking something. A Chelsea tractor is an Hausfrauenpanzer. One exception I can think of is the Rückenpanzer, or spine protector.

In a contemporary military context, a Panzer is any armoured vehicle. The definition is indeed looser than in English. The equivalent of tank (or main battle tank, MBT) is Kampfpanzer. Fighting tank.

An IFV like the M2 is a Schützenpanzer. Shooter/gunner/rifleman’s tank.

But when using Panzer to describe a specific vehicle, as opposed to a general category, I too would expect it to refer to an MBT. But I could be wrong here.