arm -- (a human limb; technically the part of the superior limb between the shoulder and the elbow but commonly used to refer to the whole superior limb)
arm, branch, limb -- (any projection that is thought to resemble a human arm; "the arm of the record player"; "an arm of the sea"; "a branch of the sewer")
weapon, arm, weapon system -- (any instrument or instrumentality used in fighting or hunting; "he was licensed to carry a weapon")
arm -- (the part of an armchair or sofa that supports the elbow and forearm of a seated person)
branch, subdivision, arm -- (a division of some larger or more complex organization; "a branch of Congress"; "botany is a branch of biology"; "the Germanic branch of Indo-European languages")
sleeve, arm -- (the part of a garment that is attached at the armhole and that provides a cloth covering for the arm)
Overview of verb arm
The verb arm has 2 senses
arm, build up, fortify, gird -- (prepare oneself for a military confrontation; "The U.S. is girding for a conflict in the Middle East"; "troops are building up on the Iraqi border")
arm -- (supply with arms; "The U.S. armed the freedom fighters in Afghanistan")