Final answer:
An antonym for pugnacious is 'peaceful' or 'congenial,' while a synonym could be 'bellicose' or 'aggressive,' representing a propensity to oppose or be combative.
Step-by-step explanation:
The antonym and synonym of pugnacious are essential to understand. To be pugnacious is to be eager or quick to argue, quarrel, or fight. Therefore, an antonym for pugnacious could be 'peaceful' or 'congenial,' as these words describe someone who is the opposite of combative or argumentative. On the other hand, a synonym for pugnacious could be 'bellicose' or 'aggressive,' which suggests someone who might oppose others in an argumentative or combative manner.