arm

Concise Oxford English Dictionary © 2008 Oxford University Press:
arm1

▶noun

• 1 each of the two upper limbs of the human body from the shoulder to the hand.

  ■ a limb of an octopus, starfish, or other animal.

• 2 a side part of a chair supporting a sitter's arm.

• 3 a narrow strip of water or land projecting from a larger body.

• 4 a branch or division of an organization.

• 5 Mathematics each of the lines enclosing an angle.

– phrases
arm in arm with arms linked.
cost an arm and a leg informal be extremely expensive.
would give one's right arm for informal wish for desperately.
in arms (of a baby) too young to walk.
keep at arm's length avoid intimacy or close contact with.
the long (or strong) arm of the law the far-reaching power of the law.
with open arms with great affection or enthusiasm.

– derivatives
armful noun (pl. armfuls),
armless adjective,
armload noun.

– origin OE arm, earm, of Gmc origin.

Concise Oxford English Dictionary © 2008 Oxford University Press:
arm2

▶verb

• 1 supply with weapons.

  ■ provide with essential equipment or information for a task or situation.

• 2 activate the fuse of (a bomb) so that it is ready to explode.

– origin ME: from OFr. armer, from L. armare, from arma ‘armour, arms’.