arm

1 arm /ˈɑɚm/ noun
plural arms
1 arm
/ˈɑɚm/
noun
plural arms
Britannica Dictionary definition of ARM
[count]
1 
: either one of the two long body parts that join the top of your body at the shoulder and that end at the hand or wrist
— see picture at human
2 
: the part of a piece of clothing (such as a shirt or coat) that covers the arm : sleeve
3 
: a part of a piece of furniture (such as a chair or couch) that gives support for a person's arm — see also 1armchair
4 
a  : a long thin piece that is connected to the main part of a machine, structure, etc., and that looks or moves like a human arm
b  : a long and narrow area of water
5 
: the part of a group or organization that performs a specific job or function — usually singular
6 
US, sports : a person's ability to throw a ball — usually singular

an arm and a leg

informal
: a very large amount of money

arm in arm

: next to each other with the arm of one person linked at the elbow to the arm of another person

a shot in the arm

— see 1shot

as long as someone's arm

— see 1long

at arm's length

: from a distance that is the length of a person's arm
◊ To keep someone or something at arm's length is to avoid being very close to or friendly with someone or something.

chance your arm

— see 2chance

give your right arm

— see 1give

the long arm of the law

: the ability of the police to find and catch people who commit crimes

twist someone's arm

— see 1twist

with open arms

: in a very kind and friendly way
2 arm /ˈɑɚm/ noun
plural arms
2 arm
/ˈɑɚm/
noun
plural arms
Britannica Dictionary definition of ARM
1 
[count] : a gun or other weapon that is used especially in a war — usually plural
— often used before another noun
— see also arms race, firearm, small arms

call to arms

◊ A call to arms is a request or command to become ready to fight.
◊ The phrase is also used for something that tries to make people fight for a cause.

in arms

◊ If someone is your brother/sister/comrade in arms, that person has helped you fight an enemy especially in a war.

lay down your arms

: to put down your weapons and stop fighting

present arms

military
— used as a command to hold your rifle so that it points straight up in front of you as a sign of respect

take up arms

: to pick up weapons and become ready to fight

under arms

: serving in the military

up in arms

: angry and ready to fight or argue
3 arm /ˈɑɚm/ verb
arms; armed; arming
3 arm
/ˈɑɚm/
verb
arms; armed; arming
Britannica Dictionary definition of ARM
1 
: to provide (yourself, a group, a country, etc.) with weapons especially in order to fight a war or battle
[+ object]
— often + with
[no object]
— opposite disarm; see also 1armed, unarmed
2 
[+ object] : to provide (someone) with a way of fighting, competing, or succeeding
3 
[+ object] : to make (a bomb, weapon, etc.) ready for use
— opposite disarm