by the backdoor

• 经后门,偷偷摸摸地； 不合法地

by the backdoor的用法和样例：

例句

1. He prowled through the house like a familiar ghost.
   他就象识途的幽灵一样，偷偷摸摸地在房子里走来走去。
2. Now they wouldn't have to socialize on the sly.
   现在他们不必偷偷摸摸地进行社交交往了。