This page deals with slang terms for a Zombie apocalypse, in the heat of the moment it's easy to garble in horror at the situation and important messages are lost so easy terms are introduced by the military which are inevitably adopted and mutated by civilians.
In art, an underpainting is an initial layer of paint applied to a ground, which serves as a base for subsequent layers of paint. Underpaintings are often monochromatic and help to define colour values for later painting.
Undercoating is an extra dollar that an auto dealership often tries to load onto you when you buy a new car. But you need not dig into your pocket for this extra. You can do the job yourself at a total cost that is a portion of what an auto repair shop will charge you. Undercoating has two advantages.