definitive UK /dɪˈfɪn.ɪ.tɪv/US /dɪˈfɪn.ə.tɪv/adjective 6noun 2forms 3 adjective6 •Determining finally, conclusive, decisive.She will have the definitive say in the matter, after consulting her board of directors. •Definite, authoritative and complete.A strict and definitive truth. — 1650 •General, not issued for commemorative purposes. •Explicitly defined. •Limiting; determining. •(no longer used) Determined; resolved.Never crave him. We are definitive. — 1603 noun2 •an ordinary postage stamp that is part of a series of all denominations or is reprinted as needed to meet demand •a word, such as a definite article or demonstrative pronoun, that defines or limits something formsdefinitives · more definitive · most definitive