backbone

UK: /ˈbækbəʊn/ US: /ˈbækˌboʊn/ ,(bak′bōn′)

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

back•bone /ˈbækˌboʊn/   n. 

1. Anatomy [countable] the spinal column;
   spine.
2. [uncountable] strength of character.
3. [countable] the main strength or support of something:
   The small farmer was the backbone of the republic.

WordReference Random House Unabridged Dictionary of American English © 2025

back•bone  (bak′bōn′), n. 

1. Anatomy the spinal column;
   spine.
2. strength of character;
   resolution.
3. something resembling a backbone in appearance, position, or function.
4. Printing [Bookbinding.] a back or bound edge of a book;
   spine.
5. Nautical, Naval Terms a rope running along the middle of an awning, as a reinforcement and as an object to which a supporting bridle or crowfoot may be attached.
6. Naval Terms the central fore-and-aft assembly of the keel and keelson, giving longitudinal strength to the bottom of a vessel.

• Middle English bacbon. See back¹, bone¹ 1250–1300

back′boned′, adj. 
back′bone′less, adj. 
Synonyms

• 2. firmness, decision, fortitude.

Collins Concise English Dictionary © HarperCollins Publishers::

backbone / ˈbækˌbəʊn/ noun

1. a nontechnical name for spinal column
2. something that resembles the spinal column in function, position, or appearance
3. strength of character; courage