uneven bars

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

• noun plural A piece of gymnastic equipment consisting of two horizontal bars set at different heights on adjustable supports and used for swinging maneuvers and transitions from one bar to the other.

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

• noun gymnastics A set of apparatus used by female gymnasts consisting of two horizontal bars at a small distance apart and set at different heights.
• noun gymnastics A gymnastics event using the uneven bars.

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

• noun a pair of parallel bars set at different heights; used in women's gymnastics