nose ring

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

• noun A ring inserted through the nose of an animal to allow the passage of a rope, as for leading or securing.
• noun A ring inserted through the nose of a person as an ornament.

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

• noun A ring affixed to the snout of cattle, to make them follow immediately when a chain is attached to the ring.
• noun A ring worn on a person's nose, for jewelry

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

• noun a ring worn on the nose as an ornament or on the nose of an animal to control it