Synonyms for Definitive (same or very similar meaning)
WordNet sense 1 (of recognized authority or excellence):
authoritative, classical
WordNet sense 2 (clearly defined or formulated):
unequivocal
WordNet sense 3 (supplying or being a final or conclusive settlement):
determinate
WordNet sense 4 (forming an end or termination; especially putting an end to doubt or question):
conclusive
From the ODE community, based on WordNet
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