(1):

(n.) Armor; whatever is worn or used for the protection and defense of the body, esp. the protective outfit of some animals and plants.

(2):

(n.) Iron bars or framing employed for the consolidation of a building, as in sustaining slender columns, holding up canopies, etc.

(3):

(n.) A piece of soft iron used to connect the two poles of a magnet, or electro-magnet, in order to complete the circuit, or to receive and apply the magnetic force. In the ordinary horseshoe magnet, it serves to prevent the dissipation of the magnetic force.

(4):

(n.) That part of a dynamo or electric generator or of an electric motor in which a current is induced by a relatively moving magnetic field. The armature usually consists of a series of coils or groups of insulated conductors surrounding a core of iron.