WordNet sense 1 (precise; explicit and clearly defined):

definite

WordNet sense 2 (characterized by quickness and firmness):

resolute

WordNet sense 3 (putting an end to all debate or action):

peremptory

WordNet sense 4 (having momentous consequences; of decisive importance):

fateful

WordNet sense 5 (having the power or quality of deciding):

crucial, determinant, determinative

WordNet sense 6 (final and deciding):

conclusive

WordNet sense 7 (forming or having the nature of a turning point or crisis):

critical