solenoid

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A current-carrying coil of wire that acts like a magnet when a current passes through it.
2. n. An assembly used as a switch, consisting of a coil and a metal core free to slide along the coil axis under the influence of the magnetic field.

Century Dictionary and Cyclopedia

1. n. A helix of copper or other conducting wire wound in the form of a cylinder so as to be nearly equivalent to a number of equal and parallel circular circuits arranged upon a common axis. The ends of the wire are brought to the middle point, and when a current is passed through the circuit the solenoid behaves, as far as external action is concerned, like a long and thin bar magnet, For this reason, such a magnet is called a solenoidal magnet; and Ampère's theory of magnetism is based on the assumption that magnets and solenoidal systems of currents are fundamentally identical.

Wiktionary

1. n. A coil of wire that acts as a magnet when an electric current flows through it
2. n. A mechanical switch consisting of such a coil containing a metal core whose movement is controlled by the current

GNU Webster's 1913

1. n. An electrodynamic spiral having the conjuctive wire turned back along its axis, so as to neutralize that component of the effect of the current which is due to the length of the spiral, and reduce the whole effect to that of a series of equal and parallel circular currents. When traversed by a current the solenoid exhibits polarity and attraction or repulsion, like a magnet.

WordNet 3.0

1. n. a coil of wire around an iron core; becomes a magnet when current passes through the coil