solenoid

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A current-carrying coil of wire that acts like a magnet when a current passes through it.
• noun 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.

from The Century Dictionary.

• noun 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.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Elec.) 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.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A coil of wire that acts as a magnet when an electric current flows through it
• noun A mechanical switch consisting of such a coil containing a metal core, the movement of which is controlled by the current

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a coil of wire around an iron core; becomes a magnet when current passes through the coil