Meaning of the word "be up to no good" in English

What does "be up to no good" mean in English? Explore the meaning, pronunciation, and specific usage of this word with Lingoland.

be up to no good

US /bi ʌp tu noʊ ɡʊd/
UK /bi ʌp tu nəʊ ɡʊd/
"be up to no good" picture

Idiom

to be doing something bad or mischievous

Example:
I saw those kids sneaking around the back of the store; they must be up to no good.
My cat has been unusually quiet all morning. I bet she's up to no good.