There are several synonyms for the term "hard shells" that are commonly used in different contexts. Some of these synonyms include carapace, exoskeleton, armor, casing, husk, and shell. These terms are often used to describe the protective outer layer of various animals and plants, such as turtles, crabs, lobsters, and nuts. Hard shells can also be used to describe the protective coverings of various objects and devices, such as phones, laptops, and helmets. Synonyms for hard shells are often used in scientific or technical contexts, as well as in creative writing, to provide more descriptive language and imagery.