backbone vs guts

backbone and guts both are nouns.

Word	Noun	Adjective	Verb	Adverb
backbone	Yes	No	No	No
guts	Yes	No	No	No

As nouns, backbone and guts are synonyms defined as:

Other synonyms of backbone include grit, gumption, moxie, sand.

backbone (noun)	guts (noun)
the part of a network that connects other networks together	fortitude and determination
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
fortitude and determination
the series of vertebrae forming the axis of the skeleton and protecting the spinal cord
a central cohesive source of support and stability