Meaning of the word "be up in arms" in English

What does "be up in arms" mean in English? Explore the meaning, pronunciation, and specific usage of this word with Lingoland.

be up in arms

US /bi ʌp ɪn ɑːrmz/
UK /bi ʌp ɪn ɑːmz/
"be up in arms" picture

Idiom

to be very angry and ready to protest strongly about something

Example:
The residents were up in arms about the proposed new factory.
My parents will be up in arms if I don't come home by midnight.