steel guitar

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

• noun An acoustic guitar with a metal resonator built into the body, often played with a slide and producing a twangy, variable tone.

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

• noun uncountable A method of playing slide guitar using a steel (a kind of slide).
• noun countable Any of several types of guitar designed to be played using this method.

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

• noun guitar whose steel strings are twanged while being pressed with a movable steel bar for a glissando effect