Merriam-Webster Collegiate Dictionary - arm

 I. noun  Etymology: Middle English, from Old English e~; akin to Latin ~us shoulder, Sanskrit irma ~  Date: before 12th century  1. a human upper limb; especially the part between the shoulder and the wrist  2. something like or corresponding to an ~: as  a. the forelimb of a vertebrate  b. a limb of an invertebrate animal  c. a branch or lateral shoot of a plant  d. a slender part of a structure, machine, or an instrument projecting from a main part, axis, or fulcrum  e. the end of a ship's yard; also the part of an anchor from the crown to the fluke — see anchor illustration  f. any of the usually two parts of a chromosome lateral to the centromere  3. an inlet of water (as from the sea)  4. a narrow extension of a larger area, mass, or group  5. power, might the long ~ of the law  6. a support (as on a chair) for the elbow and fore~  7. sleeve  8. the ability to throw or pitch a ball well; also a player having such ability  9. a functional division of a group, organization, institution, or activity the logistical ~ of the air force  • ~less adjective  • ~like adjective  II. verb  Etymology: Middle English ~en, from Anglo-French ~er, from Latin ~are, from ~a weapons, tools; akin to Latin ars skill, Greek h~os joint, arariskein to fit  Date: 12th century  transitive verb  1. to furnish or equip with weapons  2. to furnish with something that strengthens or protects ~ing citizens with the right to vote  3. to equip or ready for action or operation ~ a bomb  intransitive verb to prepare oneself for struggle or resistance ~ for combat  III. noun  Usage: often attributive  Etymology: Middle English ~es (plural) weapons, from Anglo-French, from Latin ~a  Date: 13th century  1.  a. a means (as a weapon) of offense or defense; especially fire~  b. a combat branch (as of an ~y)  c. an organized branch of national defense (as the navy)  2. plural  a. the hereditary heraldic devices of a family  b. heraldic devices adopted by a government  3. plural  a. active hostilities ; warfare a call to ~s  b. military service ARM  abbreviation adjustable rate mortgage ARM  abbreviation ~enian