noun

1. 1. an upper limb of the human body
   2. in anatomy, the part of the upper limb between the shoulder and the elbow
   3. in nontechnical use, the part of the upper limb between the shoulder and the wrist
2. anything resembling this in structure or function; esp.,
   1. the forelimb of some vertebrate animals
   2. any limb of an invertebrate animal
3. anything commonly in contact with the human arm; esp.,
   1. a sleeve of a garment
   2. a support for the arm on a chair, sofa, etc.
4. anything thought of as armlike, esp. in being attached or connected to something larger an arm of the sea, a yardarm, the arm of a balance, an arm of the government, etc.
5. power to seize, control, etc. the long arm of the law
6. ☆ Baseball, Football ability to pitch or throw a ball

Etymology: ME < OE earm; akin to L armus, Goth arms, OHG arm: see art