Backdoor
a. 秘密的
✅ 同义词
🗣️ 情景例句
Fine. How much would you like to exchange, sir?
好的。您要兑换多少呢，先生？
It takes two to tango.
一个巴掌拍不响。
Although we can't see these atoms, they really do exist.
虽然我们看不见原子，但它们的确存在。