<p><strong>Noun</strong></p><ul><li>A device for reversing the direction of a current</li><li>(In a DC motor or generator) A cylindrical ring or disk assembly of conducting members, individually insulated in a supporting structure with an exposed surface for contact with current-collecting brushes, and mounted on the armature shaft, for changing the frequency or direction of the current in the armature windings</li><li>(Mathematics) The element equal to the product of two given elements in a group multiplied on the right by the product of the inverses of the elements</li></ul>