de ‧ fin ‧ i ‧ tive AC /dɪˈfɪnətɪv, dɪˈfɪnɪtɪv/ BrE AmE adjective
1 . [usually before noun] a definitive book, description etc is considered to be the best and cannot be improved
definitive study/work/guide etc
the definitive study of Victorian railway stations
2 . a definitive agreement, statement etc is one that will not be changed:
a definitive agreement to buy the company
—definitively adverb