The noun arm has 6 senses (first 5 from tagged texts)
1. (563) 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)
2. (168) weapon, arm, weapon system -- (any instrument or instrumentality used in fighting or hunting; "he was licensed to carry a weapon")
3. (21) branch, subdivision, arm -- (an administrative division of some larger or more complex organization; "a branch of Congress")
4. (16) 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")
5. (5) arm -- (the part of an armchair or sofa that supports the elbow and forearm of a seated person)
6. 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 (first 2 from tagged texts)
1. (4) 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")
2. (1) arm -- (supply with arms; "The U.S. armed the freedom fighters in Afghanistan")