arm

A weapon, especially a firearm; often used in the plural.

"The soldiers carried their arms into battle."

A side part of a chair or sofa where one rests an arm.

"He leaned back, resting his arm on the sofa."

The upper limb of the human body, from shoulder to hand.

"She broke her left arm playing rugby."

To supply or equip someone or something with weapons.

"The rebels were armed by a foreign power."

To prepare a device or system for operation or activation.

"Remember to arm the alarm before leaving."