Definition of "definitive"

definitive

/dɪˈfɪn.ɪ.tɪv/

adjective
comparative more definitive, superlative most definitive
1. explicitly defined
2. conclusive or decisive
3. definite, authoritative and complete
  Quotations
  A strict and definitive truth.
  1650, Thomas Browne, Pseudodoxia Epidemica: […], 2nd edition, London: […] A[braham] Miller, for Edw[ard] Dod and Nath[aniel] Ekins, […]
  Some definitive […] scheme of reconciliation.
  1838, William H[ickling] Prescott, History of the Reign of Ferdinand and Isabella, the Catholic. […], volumes (please specify |volume=I to III), Boston, Mass.: American Stationers’ Company; John B. Russell
4. limiting; determining
5. (philately) general, not issued for commemorative purposes
6. (obsolete) Determined; resolved.
  Quotations
  Never crave him. We are definitive.
  c. 1603–1604 (date written), William Shakespeare, “Measure for Measure”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, [Act V, scene i], line 424
noun
plural definitives
1. (grammar) a word, such as a definite article or demonstrative pronoun, that defines or limits something
2. (philately) an ordinary postage stamp that is part of a series of all denominations or is reprinted as needed to meet demand