adjective
An adjective is a word that describes or gives more information about a noun. In this case, 'outermost' describes the noun it is referring to as being the farthest from the center or core.
The outermost layer of the skin is called the epidermis.
The outermost shelf in the fridge is where I keep the drinks.
I always make sure to park in the outermost spot to avoid dings on my car.
His outermost layer of defense was breached, leaving him vulnerable.