a stiff hollow protective spine on a porcupine or hedgehog | a sharp rigid animal process or appendage; as a porcupine quill or a ridge on a bone or a ray of a fish fin |
the hollow spine of a feather | the part of a book's cover that encloses the inner side of the book's pages and that faces outward when the book is shelved |
any of the larger wing or tail feathers of a bird | the series of vertebrae forming the axis of the skeleton and protecting the spinal cord |
pen made from a bird's feather | a small sharp-pointed tip resembling a spike on a stem or leaf |
| any sharply pointed projection |