You use defensive to describe things that are intended to protect someone or something.
The Government hastily organized defensive measures, deploying searchlights and anti-aircraft guns around the target cities.
政府匆忙布置了防御措施,在目标城市周围部署了探照灯和高射炮。
Someone who is defensive is behaving in a way that shows they feel unsure or threatened.
Like their children, parents are often defensive about their private lives.
像子女一样,家长们通常也很注重保护他们的私生活。
In sports, defensive play is play that is intended to prevent your opponent from scoring points against you.
I'd always played a defensive game, waiting for my opponent to make a mistake.
我总是打防守战,等着对手出错。
on the defensive
If someone is on the defensive, they are trying to protect themselves or their interests because they feel unsure or threatened.
The administration has been on the defensive about the war.
政府一直在为战争辩解。