Definitions of arm:

• noun:   the part of an armchair or sofa that supports the elbow and forearm of a seated person
• noun:   any projection that is thought to resemble an arm

  Example: "The arm of the record player"

• noun:   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
• noun:   the part of a garment that is attached at armhole and provides a cloth covering for the arm
• noun:   any instrument or instrumentality used in fighting or hunting
• noun:   an administrative division of some larger or more complex organization
• verb:   supply with arms

  Example: "The U.S. armed the freedom fighters in Afghanistan"

• verb:   prepare oneself for a military confrontation
• name:  A surname (very rare: popularity rank in the U.S.: #75381)