Meaning of “go back on sth” - Learner’s Dictionary

go back on sth

phrasal verb with go uk us /ɡəʊ/ verb [ I ] (present participle going, past tense went, past participle gone)

to not do something that you promised you would do:

I never go back on my word (= not do what I said I would do).

(Definition of “go back on sth” from the Cambridge Learner’s Dictionary © Cambridge University Press)