From Longman Dictionary of Contemporary Englisharmsarms[plural]WEAPON weapons used for fighting wars Sales of arms to the Middle East have dramatically increased.nuclear arms the arms trade an arms dealer The government is cutting arms expenditure. The United Nations will lift its arms embargo against the country.take up arms (against somebody) (=get weapons and fight) Boys as young as 13 are taking up arms to defend the city. He appealed for the rebels to lay down their arms (=stop fighting).under arms (=with weapons and ready to fight) All available forces are under arms. → small arms at small1(15) → arm
Examples from the Corpus
under arms• We lay under arms all day and made but little change in our position.• About I m men are still under arms because, says the government, the war is not yet over.armsarms[plural]SIGN/INDICATION a set of pictures or patterns, usually painted on a shield, that is used as the special sign of a family, town, university etc SYN coat of arms → arm 