spine

UK: /ˈspaɪn/ US: /spaɪn/ ,(spīn)

WordReference Random House Learner's Dictionary of American English © 2025

spine /spaɪn/   n. 

1. Anatomy [countable] the backbone;
   spinal column.
2. Botany [countable]
   • a hard, sharp-pointed outgrowth on a plant;
     thorn.
   • a stiff-pointed bone or part of a bodily structure of an animal, such as the quill of a porcupine.
3. [uncountable] courage;
   mettle.
4. Printing [countable] the back of a book binding, usually indicating the title and author.

spin•y, adj., -i•er, -i•est:

I stuck my finger on one of the fish's spiny fins.

WordReference Random House Unabridged Dictionary of American English © 2025

spine  (spīn), n. 

1. Anatomy, Zoology the spinal or vertebral column;
   backbone.
2. Anatomy, Zoology any backbonelike part.
3. Zoology a stiff, pointed process or appendage on an animal, as a quill of a porcupine, or a sharp, bony ray in the fin of a fish.
4. something, as a quality or trait, that constitutes a principal strength;
   resolution;
   stamina;
   backbone:
   a situation that would test a person's spine.
5. a ridge, as of ground or rock.
6. Botany a sharp-pointed, hard or woody outgrowth on a plant;
   thorn.
7. Printing [Bookbinding.] the back of a book cover or binding, usually indicating the title and author.

• Latin spīna thorn, backbone
• late Middle English 1400–50

spined, adj. 
spine′like′, adj. 

Collins Concise English Dictionary © HarperCollins Publishers::

spine / spaɪn/ noun

1. the spinal column
2. the sharply pointed tip or outgrowth of a leaf, stem, etc
3. a hard pointed process or structure, such as the ray of a fin, the quill of a porcupine, or the ridge on a bone
4. the back of a book, etc
5. a ridge, esp of a hill
6. strength of endurance, will, etc
7. anything resembling the spinal column in function or importance; main support or feature

Etymology: 14th Century: from Old French espine spine, from Latin spīna thorn, backbone

spined adjective