Final answer:
An extremophile is a microorganism that resists and has a hard, shell-like outer covering.
Step-by-step explanation:
A microorganism that is resisting and has a hard, shell-like outer covering is called an extremophile. Extremophiles are organisms, usually microbes, that can tolerate or even thrive in conditions that are considered hostile to most life forms. These conditions can include high or low temperature, acidity, and other extreme environments.