Under arms means: Equipped with weapons (of a country, army etc.); in a state of armed, military readiness.. It is military jargon and mostly appears in service contexts, war fiction, or among veterans and their families. There is no real cause for parental concern; it is descriptive vocabulary rather than risky behaviour. If your teen uses it, context will usually make the intent clear. A short, curious question about where they heard it is usually all that is needed to know whether to follow up.
under arms
(military) Equipped with weapons (of a country, army etc.); in a state of armed, military readiness.
Definitions
Australia
#1·Apr 27, 2026AUS
(military) Equipped with weapons (of a country, army etc.); in a state of armed, military readiness.
For parents
Under arms means: Equipped with weapons (of a country, army etc.); in a state of armed, military readiness.. It is military jargon and mostly appears in service contexts, war fiction, or among veterans and their families. There is no real cause for parental concern; it is descriptive vocabulary rather than risky behaviour. If your teen uses it, context will usually make the intent clear. A short, curious question about where they heard it is usually all that is needed to know whether to follow up.
For ESL learners
under arms means: Equipped with weapons (of a country, army etc.); in a state of armed, military readiness.. Register: informal, military jargon. A common learner mistake is using the word in a register it does not fit, or assuming a single global meaning; native speakers immediately notice when slang appears in formal contexts, so always check the surrounding register before producing it yourself.
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Australia
#2·Apr 27, 2026AUS
(chiefly, Australia) Carrying a weapon (chiefly of a criminal); of a crime, committed using a weapon or weapons.
Cluster: violence
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For specific readers
Why is this section here?
Slang is read by different audiences for very different reasons. The For parents view re-explains the term in plain, non-judgemental language so a caregiver can understand what their child means without needing the surrounding subculture. The For English learners view focuses on register (when it's safe to use), formal alternatives, and common mistakes — what a textbook won't teach you.
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Australia
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