noun

• (anatomy, zootomy) A series of bones situated at the back from the head to the pelvis of a human, or from the head to the tail of an animal, enclosing the spinal cord and providing support for the thorax and abdomen.
• (figurative) Courage or assertiveness.
• Something resembling a backbone, such as a ridge, or a long, central structure from which other structures radiate.
• The narrow, bound edge of a book that encloses the inner edges of the pages, facing outwards when the book is on a shelf and typically bearing the title and the author's and publisher's name.
• (zootomy, botany) A pointed, fairly rigid protuberance or needlelike structure on an animal, shell, or plant.
• (botany) The heartwood of trees.
• A linear payscale operated by some large organizations that allows flexibility for local and specific conditions.
• (geology) A tall mass of viscous lava extruded from a volcano.
• The stiffness of an arrow.
• (neuroscience) Ellipsis of dendritic spine.. [A small membranous protrusion from the dendrite of a neuron that typically receives input from a single axon at the synapse.]