adjective Having the power or quality of deciding a question or controversy; putting an end to contest or controversy; final; conclusive.
decisive vote
adjective Decided; definite; incontrovertible.
decisive victory
adjective Marked by promptness and decision, resolute; without hesitation.
decisive action
adjective ↑ Hurd, Seth P. (1847), “Decisive”, in “False Pronunciation”, in A Grammatical Corrector; or, A Vocabulary of the Common Errors of Speech, Philadelphia: E. H. Butler & Co, →OCLC, page 80.