impossible to guard against 防不胜防

“防不胜防”，汉语成语，意思是想防备但防备不过来。可以翻译为“impossible to guard against，preventive measures prove to be useless或no way to prevent”等。

例句：

他球路多变，令对手防不胜防。

His opponent couldn't stand up to his varied and fast-changing tactics.

各种诈骗手段让人防不胜防。

Various deceptive means are hardly preventable.