laborious vs backbreaking

laborious and backbreaking both are adjectives.

Word	Noun	Adjective	Verb	Adverb
laborious	No	Yes	No	No
backbreaking	No	Yes	No	No

As adjectives, laborious and backbreaking are synonyms defined as:

laborious and backbreaking: characterized by effort to the point of exhaustion; especially physical effort

Other synonyms of laborious include arduous, grueling, gruelling, hard, heavy, operose, punishing, toilsome.

laborious (adjective)	backbreaking (adjective)
characterized by effort to the point of exhaustion; especially physical effort	characterized by effort to the point of exhaustion; especially physical effort