up to mischief

基本解释

Have you been up to mischief again?
你是不是又捣蛋了？
They look cute, but they are often up to mischief.
他们看起来很聪明，但是他们经常恶作剧。
33ff.net
Given an unusual amount of free time on their hands outside of working hours, with little in the way of entertainment options, some delegates got up to mischief.
由于在工作之外拥有了大把的业余时间，再加上没有什么可以选择的娱乐项目，于是某些美国代表就开始搞恶作剧。

And now in the 21st century, they are up to mischief.
FORBES: Mr. Market Will Get His Pound Of Flesh...And Then Some
Classic Halvorsen mischief was to come up with a cover design for one issue that parodied Business Week.
FORBES: Sidelines
Researchers at the Black Hat conference showed just what mischief a commonly used UK PoS terminal could get up to when they inserted a chip-and-pin card crafted with malicious code.
ENGADGET: Security experts hack payment terminals to steal credit card info, play games