It's a good question. But, I don't think it has a specific name. (I'm happy to be corrected.)
You see, in English, words can switch roles between the different parts of speech easily (and without changing). It's one of the reasons why English is so easy to speak compared to other languages.
For example:
It is a car door.
Car is a noun, but here it's being used as an adjective.
I know this is a simple example, but it's the same point.