When it comes to describing objects or animals that have a tough exterior, "hard-shelled" often comes to mind. However, there are a variety of synonyms that can be used to convey a similar meaning. Some options include "armor-plated," "sturdy," "durable," "unyielding," "reinforced," and "fortified." These words can be used to describe everything from tortoise shells to armored vehicles. It's important to choose the right synonym based on the context of the sentence and the specific object or animal being described. By incorporating a variety of descriptive words, writers can create vivid and engaging content that captivates their readers.