What does exoskeleton mean?
An exoskeleton is a rigid, external structure that supports and protects the bodies of many animals, most famously arthropods such as insects, crabs, lobsters, and spiders. Typically made of tough materials like chitin or calcium carbonate, it serves as armor against predators and as a framework for muscle attachment, since these animals lack internal bones. Because it cannot expand, an animal with an exoskeleton must periodically molt — shedding the old shell while a new one hardens — a vulnerable stage in its life cycle. In modern usage, the word has expanded beyond biology: engineers now build powered exoskeletons, wearable frames that augment human strength or restore mobility in medicine and industry. Whether describing a beetle's armored shell or a robotic assistive suit, "exoskeleton" captures the idea of strength drawn from a structure on the outside of the body rather than within it.
nounA rigid external covering or supportive structure that encases and protects the body of certain animals, such as insects, crustaceans, and other arthropods.
- A rigid external covering that supports and protects the bodies of arthropods such as insects, crustaceans, and spiders.
- (Extended use) An external structural frame worn or attached to a body, especially a powered suit that augments human strength or mobility in robotics and medicine.
"The crab's tough exoskeleton shields it from predators, but the animal must shed it in order to grow."
"An insect's exoskeleton must be molted periodically to allow the animal to grow."
"Engineers have developed powered exoskeletons that help paralyzed patients walk again."
The standard plural is regular. It commonly appears in biological and engineering contexts when discussing multiple animals or multiple devices.
"Beetles are among the most successful animals on Earth, protected by their durable exoskeletons."
Every crab you've ever eaten once crawled out of its own exoskeleton and grew a brand-new one — a process called molting that arthropods repeat throughout their lives.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of exoskeleton
The word "exoskeleton" combines the Greek prefix "exo-", meaning "outer" or "outside," with "skeleton," which derives ultimately from the Greek "skeletos," meaning "dried up" or "hardened." It was coined in the nineteenth century as zoologists formalized the comparative anatomy of arthropods, contrasting animals whose supportive frameworks lie outside the body with those possessing internal skeletons. The same Greek root "exo-" appears in English words such as "exothermic" and "exoplanet," all sharing the sense of "outside" or "external."
Related word forms
How exoskeleton is actually used
"Exoskeleton" is a technical term common in biology and zoology, but it has entered general usage through popular science and robotics reporting, where it often refers to wearable assistive frames rather than animal anatomy. The extended robotic sense is well established but distinct from the original biological one.
Easily confused with exoskeleton
An endoskeleton is an internal supporting framework (as in vertebrates), whereas an exoskeleton is a hard covering on the outside of the body.