spine

noun

• 1a series of vertebrae extending from the skull to the small of the back, enclosing the spinal cord and providing support for the thorax and abdomen; the backbone.
• a thing’s central feature or main source of strength:players who will form the spine of our team
• resolution or strength of character.
• the part of a book’s jacket or cover that encloses the inner edges of the pages, facing outward when the book is on a shelf and typically bearing the title and the author’s name.

• 2 Zoology & Botany any hard pointed defensive projection or structure, such as a prickle of a hedgehog, a spikelike projection on a sea urchin, a sharp ray in a fish’s fin, or a spike on the stem of a plant.
• Geology a tall mass of viscous lava extruded from a volcano.