althorn

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

• noun Any of several upright, valved brass wind instruments used especially in bands.

from The Century Dictionary.

• noun A musical instrument of the sax-horn class, often used in place of or with the French horn in military bands.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Mus.) An instrument of the saxhorn family, used exclusively in military music, often replacing the French horn.

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

• noun music An alto or tenor saxhorn