arm

³arm

noun, often attributive

Definition of ARM

1

a : a means (as a weapon) of offense or defense; especially : firearm b : a combat branch (as of an army) c : an organized branch of national defense (as the navy)

2

plural a : the hereditary heraldic devices of a family b : heraldic devices adopted by a government

3

plural a : active hostilities : warfare <a call to arms> b : military service

— up in arms

: aroused and ready to undertake a fight or conflict <voters up in arms over the proposed law>

Origin of ARM

Middle English armes (plural) weapons, from Anglo-French, from Latin arma

First Known Use: 13th century