standing wave

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

• noun A wave that oscillates in place and creates stable nodes of maximum and zero oscillation, produced whenever a wave is confined within boundaries, as in the vibrating string of a musical instrument.

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

• noun A wave form which occurs in a limited, fixed medium in such a way that the reflected wave coincides with the produced wave. A common example is the vibration of the strings on a musical stringed instrument.

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

• noun a wave (as a sound wave in a chamber or an electromagnetic wave in a transmission line) in which the ratio of its instantaneous amplitude at one point to that at any other point does not vary with time