A French horn.
French horn definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
a brass instrument with a mellow tone, consisting of a long, spiral tube ending in a flaring bell, three valves, and a funnel-shaped mouthpiece: horn is the term preferred by musicians playing classical music
French horn definition by American Heritage Dictionary
nounThe American Heritage® Dictionary of the English Language, 4th edition Copyright © 2010 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
A valved brass wind instrument that produces a mellow tone from a long narrow tube that is coiled in a circle before ending in a flaring bell.