Quick answer: “Up in arms” means very angry and ready to protest strongly.
Up in arms — Very angry and ready to protest strongly about something, often as a group.
Origin & History
The phrase originates from a literal military sense: 'in arms' meant armed and ready for battle, and to be 'up in arms' meant to have risen in armed rebellion.
Over time, the expression softened to describe strong verbal protest and anger rather than literal armed conflict, and it is now used for any group reaction of outrage. Learners who want to check other figurative expressions can consult general reference works such as the Cambridge Dictionary, which document how such idioms are used today.
Example Sentences
| Sentence | Context |
|---|---|
| Residents were up in arms about the proposed new road. | Community protest |
| Parents were up in arms over the school's decision to cut music classes. | Education |
| Staff were up in arms when the bonus was cancelled. | Workplace |
| Fans were up in arms about the ticket price increase. | Sport/entertainment |
Dialogue Example
A: Why is everyone at the office so tense today?
B: Staff are up in arms about the new parking policy.
Common Mistakes
Mistakes to Avoid
He was up in arm about the decision.
He was up in arms about the decision. — The fixed phrase uses the plural 'arms'.
They were up on arms.
They were up in arms. — The correct preposition is 'in', not 'on'.
The protesters were literally up in arms with weapons.
In modern usage, the idiom means angry and protesting, not literally carrying weapons.
Similar Idioms
Practise This Idiom
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Quick Check: Up in arms
2 questions — test what you just learned.
1. What does “Up in arms” mean?
2. Complete the sentence: “Residents were _____ about the proposed new road.”
Frequently Asked Questions
What does "up in arms" mean?
"Up in arms" means very angry and ready to protest strongly about something, often as a group.
Where does "up in arms" come from?
It comes from a literal military sense, where 'in arms' meant armed for battle. The expression softened over time to mean strong protest rather than literal fighting.
Can you give an example of "up in arms" in a sentence?
"Residents were up in arms about the proposed new road." It is used to describe collective anger and protest.
Is "up in arms" formal or informal?
It is neutral to semi-formal and common in journalism, news reports, and everyday conversation.
What CEFR level is "up in arms"?
This idiom is typically taught at B2 level, as it originates from a historical military reference.
What are common mistakes with "up in arms"?
Common mistakes include using the singular 'arm' instead of 'arms', or the wrong preposition 'on arms'.
What idioms are similar to "up in arms"?
Similar idioms include: Hopping mad, Hit the roof, Up in revolt. These describe strong collective anger.
How do I practise idioms like "up in arms"?
Try LexFizz's Flash Cards and Flip Tiles, and describe a news story where people were up in arms about something.
Can "up in arms" be used in writing?
Yes, it is very common in journalism and news reports describing public reaction and protest.
Does "up in arms" have the same meaning in British and American English?
Yes, it is understood identically in both, and is widely used across all major varieties of English.