ˈkɹɪtɪkəl dɪˈsaɪsɪv forming or having the nature of a turning point or crisis a critical point in the campaign the critical test determining or having the power to determine an outcome cast the decisive vote two factors had a decisive influence characterized by decision and firmness an able and decisive young woman we needed decisive leadership she gave him a decisive answer unmistakable had a decisive lead in the polls